In a primary race largely dominated by the popularity of President Donald Trump among Alabama Republicans, three GOP candidates will square off Tuesday in a special election primary to fill the Senate seat vacated by Attorney General Jeff Sessions. 
 
 After weeks of vowing to remain on the sidelines, Trump inserted himself front-and-center in the race earlier this month when he endorsed Sen. Luther Strange, who was appointed to fill Sessions' seat temporarily earlier this year. On Monday, news emerged that the president had begun recording robocalls for him, urging Alabama GOP voters to support him. 
 
 But the other two candidates have sought to suggest no daylight between them and the president, either. 
 
 Twice-elected, twice-deposed Chief Justice of the Alabama Supreme Court Roy Moore, Tea Party favorite Rep. Mo Brooks, R-Ala, and Strange have duked it out for months, competing for the attention of voters who still hold the president in extremely high regard. 
 
 Moore has a steady lead in most polls, but has fallen short of the 50-percent mark, pitting Strange and Brooks in a battle for second place. 
 
 If no candidate hits 50 percent on Tuesday, only the top two candidate will move on to a runoff on Sept. 26, before the general election in December. 
 
 Sen. Luther Strange, R-Ala., responds to questions during a television interview on Capitol Hill on July 11. J. Scott Applewhite / AP 
 
 A senior Alabama GOP official told NBC News last week following Trump’s endorsement that the president’s move was “monumental,” and said that if Strange does better than the polls suggest, it would indicate Trump still holds substantial sway in the Yellowhammer State. 
 
 "If [Strange] is No. 1 one in the runoff, there’s the story," the official said. 
 
 But if Strange doesn’t make the runoff, it could erode the narrative of Trump’s influence in the state, the official said. 
 
 Adding even more uncertainty around Tuesday’s outcome is the fact that both Strange and Brooks, whose congressional district runs along the state’s northern border, head into the race carrying baggage. 
 
 Alabama Rep. Mo Brooks announces his candidacy for the U.S. Senate in Huntsville, Alabama on May 15, 2017. Bob Gathany / AL.com via AP file 
 
 Strange has been dogged by questions about his appointment to Sessions' seat by former Gov. Robert Bentley, who was shortly thereafter driven out of office by a sex scandal, while Brooks attracted negative attention himself for running a campaign ad using audio from the June shooting that injured House Majority Whip Steve Scalise (R-La.). Brooks attended the practice. 
 
 Strange has also received support from Senate Majority Leader Mitch McConnell, R-Ky. and a McConnell-affiliated super PAC said in July it would spend up to $10 million on the race. Brooks — who trailed Strange in a poll released last week 18 percent to 23 percent — has tried to use that against his competitor, ripping him repeatedly as the “establishment” candidate. 
 
 Alabama Chief Justice Roy Moore poses in 2015. Brynn Anderson / AP file 
 
 Meanwhile, on the Democratic side, a man named Robert Kennedy Jr. (no, not that Robert Kennedy, Jr.) is crushing his next closest competitor in the polls, seemingly enjoying an advantage of his famous-sounding name. 
 
 Kennedy, who shares no relation to the Kennedy political dynasty, remains at the top of the seven-candidate Democratic field, according to a poll released in late July commissioned by Birmingham TV station WBRC, one of the only surveys of the race. 
 
 Among those trailing Kennedy's 49-percent support in that poll — which would put him just short of avoiding a runoff — is Doug Jones, a former U.S. attorney appointed by Bill Clinton who has been involved in Alabama politics since he was president of the Young Democrats chapter in law school. 
 
 Robert Kennedy Jr. speaks during a Democratic Senate candidate forum at the Princess Theatre on August 3, 2017 in Decatur, Alabama. file Jeronimo Nisa / The Decatur Daily via AP file 
 
 Kennedy has been dubbed by local papers as a “mystery candidate" and campaign finance reports show that, by the end of June, he hadn’t hired any staff or spent any money on anything other than online fundraising processing fees. 
 
 He told NBC News earlier this month that he’s a gun-owning fiscal conservative who emphasizes "faith," "family," and "freedom,” who nevertheless is pushing for an activist federal government. 
 
 But even if Kennedy cruises, he faces a near-impossible path to victory in a general election against the eventual Republican candidate. Alabama voters haven’t elected a Democrat to the U.S. Senate since 1992 and haven’t elected a Democratic governor since 1998. ||||| The Alabama GOP Senate primary on Tuesday will go a long way in answering the overriding question of the race: How much do Mitch McConnell’s cash and Donald Trump’s endorsement matter? 
 
 The brutal fight on the Republican side is all but assured to go to a September runoff, with no one expected to reach the 50 percent threshold to win the nomination outright. Sen. Luther Strange has the backing of Trump — who remains immensely popular in Alabama and cut a robocall for the senator on Monday — and millions in ads from a McConnell-blessed super PAC. 
 
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 Even with that help, Strange isn't a lock to secure a spot in the runoff. Polls show ex-state Supreme Court Justice Roy Moore consistently leading, while Strange and Rep. Mo Brooks are battling for the runner-up position. 
 
 The polls close at 8 p.m. ET (7 p.m. local time). Here are POLITICO’s five things to watch as Moore, Strange and Brooks vie for the top two slots to advance to the Sept. 26 runoff: 
 
 Where does Strange land — and what does it mean? 
 
 With a massive cash advantage, powerhouse endorsements and the advantages of incumbency, Strange should be the front-runner. But swirling questions about how he was appointed to the seat by the disgraced ex-Gov. Robert Bentley have dogged Strange throughout his campaign. 
 
 “Luther Strange is the first opportunity voters have to put a head on a spike for all the corruption that’s been going on in Republican politics in the last three years," one former Alabama GOP official said. 
 
 Strange denies any impropriety and instead touts his record of taking on corruption as the twice-elected state attorney general. 
 
 But should Strange somehow not make the runoff — he's consistently placed second in polls, though the margin between him and Brooks is narrow — it would be a huge embarrassment for McConnell and establishment Republicans who have invested millions to help Strange secure the nomination. 
 
 Will Trump’s endorsement amount to anything? 
 
 In a race in which the candidates have tripped over each other trying to align themselves with the president, Strange can proudly claim he is Trump's man. 
 
 Trump announced the endorsement in a surprise tweet last week, tweeted again on Monday to boost the senator and recorded a robocall to help get out the vote on Election Day. 
 
 How much Trump’s imprimatur matters is unclear, but Strange isn’t hesitating to remind voters of it at every turn. 
 
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 To a crowd of Republicans in Homewood, Alabama last week, Strange recounted the phone call with Trump when he informed the senator of the endorsement, when the president told him: “I’ve never done this in a contested primary before, I’m sure I’m going to be criticized, but it’s important to get my agenda passed and I appreciate what you’re going through to get it done.” 
 
 “So, I can’t say anything more than what the president himself has said,” Strange told local party activists in the Birmingham suburb. “I hope you will bear that in mind.” 
 
 How high does Moore go? 
 
 Virtually every poll has shown Moore making the runoff by a comfortable margin. A trio of recent surveys had the judge leading the field with support in the 31 to 35 percent range. 
 
 Rep. Mo Brooks (left) is battling for the runner-up position in the Alabama GOP primary; polls show ex-state Supreme Court Justice Roy Moore (right) consistently leading. | AP Photos 
 
 Republican officials expect turnout to be low, which would likely hurt the rest of the field but potentially boost Moore, given his enthusiastic base. At the same time, Moore’s campaign is floating the idea that he could exceed expectations and win somewhere above 35 percent but probably below the 50 percent needed to clinch the nomination outright. 
 
 Moore’s campaign is also banking on Trump’s endorsement making only a marginal difference in the primary. 
 
 “I’m sure it’s got some effect on some people but I don’t sense the folks I’m talking to are being moved by it,” said Moore campaign chairman Bill Armistead. "I think the die is pretty well cast.” 
 
 What does the outcome signal for the runoff? 
 
 Strange is struggling even with the support of the president and the GOP establishment. Assuming he makes it to the runoff, though, the strength of his second-place finish will set expectations for how winnable the election is — or not. 
 
 If Strange barely makes it into the runoff — or comes in third — it will call into question the influence of Trump’s support in a reliably Republican state. If Strange exceeds the low 20-percent support he's gotten in recent polls, he'll still face a tough battle against Moore but won’t have to field a wave of questions about his ultimate viability or the power of Trump's endorsement. 
 
 What about the Democratic primary? 
 
 A Democrat hasn’t held a U.S. Senate seat in Alabama since 1997 but the party feels it might have an outside shot if the chips all fall its way. 
 
 Seven candidates are running for the Democratic nomination, but two are really in play: former U.S. attorney Doug Jones and Robert Kennedy Jr., a Navy veteran and business executive who’s unrelated to the Kennedy family. 
 
 Jones is the favorite of the Democratic establishment and has been endorsed by former Vice President Joe Biden as well as a handful of members of Congress. Democrats hope Jones’ civil rights records, including being the federal prosecutor who convicted two Klansmen involved in the 1963 16th Street Baptist Church bombing, and a chaotic Republican primary will create an opening for the seat. 
 
 A Raycom News Network and Strategy Research poll released in late July found Kennedy leading the Democratic field with 49 percent support and Jones in second place with 28 percent. This was before the endorsement by Biden, who has strong ties to Southern Democrats, but Jones’ campaign is still bracing for a tight election night and a likely runoff battle ahead. ||||| Former Alabama Chief Justice and U.S. Senate candidate Roy Moore walks off the stage Monday, Sept. 25, 2017, in Fairhope, Ala. (AP Photo/Brynn Anderson) (Associated Press) 
 
 MONTGOMERY, Ala. (AP) — The Latest on Alabama's GOP primary (all times local): 
 
 8:50 p.m. 
 
 Incumbent Sen. Luther Strange wished jurist Roy Moore well after losing the Alabama Republican primary for Senate. 
 
 Strange told his supporters Tuesday night that "we wish (Moore) well going forward." 
 
 But he quickly shifted to his own bewilderment at the race he just finished. "We're dealing with a political environment that I've never had any experience with," he said. 
 
 "I'm telling you, the political seas and winds in this country right now ... are very hard to navigate, very hard to understand." 
 
 Strange also thanked President Donald Trump and Vice President Mike Pence for backing him. 
 
 Strange said Trump, may "be criticized" for coming to Alabama on his behalf. "Sometimes it's just about friendship ... a common goal to make the country better," he said. 
 
 ___ 
 
 8:45 p.m. 
 
 A group that put millions of dollars behind Sen. Luther Strange in Alabama's Senate race says it will now back Roy Moore. 
 
 Senate Leadership Fund President and CEO Steven Law said Tuesday that Moore won the nomination "fair and square." 
 
 Law says Moore "has our support, as it is vital that we keep this seat in Republican hands." 
 
 The group, which has ties to Senate Majority Leader Mitch McConnell, put millions of dollars behind Strange in the heated GOP primary with Moore. 
 
 Moore will face Democrat Doug Jones in December. 
 
 ___ 
 
 8:25 p.m. 
 
 Firebrand jurist Roy Moore has won the Alabama Republican primary for U.S. Senate, defeating an appointed incumbent backed by President Donald Trump and allies of Sen. Mitch McConnell. 
 
 In an upset likely to rock the party establishment, Moore clinched victory Tuesday over Sen. Luther Strange to win the GOP nomination for the Senate seat previously held by Attorney General Jeff Sessions. Moore will face Democrat Doug Jones in a Dec. 12 special election. 
 
 Moore is the state's former chief justice who was twice removed from his duties for defying federal courts over same-sex marriage and the public display of the Ten Commandments. 
 
 Propelled by evangelical voters, Moore consolidated support from a number of anti-establishment forces, including former White House strategist Steve Bannon. 
 
 ___ 
 
 8:10 p.m. 
 
 Alabama Sen. Luther Strange has yet to appear at his election night party where several dozen of his supporters are gathering to watch early returns showing Strange trailing Roy Moore in a U.S. Senate primary runoff. 
 
 Strange's supporters were late arrivals to the suburban Birmingham hotel, and many are quietly watching returns and suggesting that Moore's wide leads in many counties will be too much for Strange to overcome. 
 
 Strange is watching returns privately. 
 
 He was appointed to the seat earlier this year when Jeff Sessions won confirmation as the nation's attorney general. 
 
 ____ 
 
 7:55 p.m. 
 
 Former Alabama Chief Justice Roy Moore entered his election night party to applause from supporters optimistic that he will win the GOP nomination for U.S. Senate. 
 
 Moore smiled broadly Tuesday evening as he exchanged handshakes and hugs from supporters. He did not speak to the crowd. 
 
 He will watch returns in a room in another part of the building. 
 
 Moore is competing against incumbent Sen. Luther Strange for the nomination for Attorney General Jeff Sessions' former Senate seat. 
 
 Former University of Alabama running back Siran Stacy, who is now a pastor, led the crowd in a prayer as they held their hands up in worship, and a hymn. 
 
 The crowd applauded as the first results showed Moore leading in rural counties. 
 
 ___ 
 
 7:05 p.m. 
 
 Polls have closed in Alabama's Republican Senate primary runoff. 
 
 Voting ended 7 p.m. Tuesday in the race to fill Attorney General Jeff Sessions' former Senate seat. 
 
 U.S. Sen. Luther Strange and firebrand jurist Roy Moore are competing in the Alabama's GOP primary that has pitted President Donald Trump against a former top adviser. 
 
 Trump is backing Strange. Former White House strategist Steve Bannon is supporting Moore. Moore's campaign chairman said Bannon is expected to attend Moore's election night party in Montgomery, Alabama. 
 
 The winner faces Democrat Doug Jones in December. 
 
 ___ 
 
 3:30 p.m. 
 
 Sen. Luther Strange is urging voters to get the polls in Alabama's heated GOP runoff for the Senate seat. 
 
 "President Donald Trump needs you NOW!" the campaign wrote in a Tuesday message that was emailed to supporters at midday. The campaign urged people to get to the polls before they close at 7 p.m. 
 
 His campaign has emphasized his endorsement from Trump. 
 
 Strange voted early Tuesday morning in the race where he faces former state chief justice Roy Moore. Strange then greeted breakfast diners at nearby restaurants. 
 
 ___ 
 
 2:15 p.m. 
 
 Alabama Secretary of State John Merrill says turnout for the state's Republican runoff for U.S. Senate is so far looking pretty low. 
 
 Merrill said he was projecting a 12 to 15 percent turnout for Tuesday's race. 
 
 Sen. Luther Strange and Alabama Chief Justice Roy Moore are vying for the Republican nomination for the Senate seat that belonged to U.S. Attorney General Jeff Sessions. 
 
 Low turnout is largely considered to be positive for Moore, who has a loyal following among state evangelical voters. 
 
 Moore led Strange by about 25,000 votes in the crowded August primary, and runoff polls have shown him leading or in a dead heat with Strange. 
 
 Turnout for the August primary was 17 percent. 
 
 ___ 
 
 11:45 a.m. 
 
 Alabama Senate candidate Roy Moore has cast his ballot after riding a horse to his rural polling place in northeastern Alabama. 
 
 Moore wore a short-sleeve shirt and a white cowboy hat Tuesday morning as he climbed off his mount outside the Gallant Volunteer Fire Department. 
 
 Accompanied by relatives, he chatted with fellow voters and marked his ballot in the tiny precinct. 
 
 Moore and appointed Sen. Luther Strange are vying for the U.S. Senate seat previously held by U.S. Attorney General Jeff Sessions. Strange voted earlier in suburban Birmingham. 
 
 Moore says riding a horse to vote is an Election Day tradition for him. His house is near his polling place. 
 
 ___ 
 
 8 a.m. 
 
 Alabama Sen. Luther Strange is billing himself as the "true conservative" as voters go to the polls in the state's special GOP primary runoff election. 
 
 Strange called a supportive conservative talk show on Birmingham's WERC radio after voting Tuesday. He made a final plea for support in his race against former Alabama Chief Justice Roy Moore. 
 
 Moore is casting Strange as being part of the problem in Washington since he's supported by the GOP establishment. But Strange denies that and says he's only trying to get President Donald Trump's agenda passed through Congress. 
 
 A super PAC aligned with Senate Majority Leader Mitch McConnell of Kentucky has pumped millions of dollars into the Alabama race on behalf of Strange. But Strange says he only met McConnell a few months ago and denies being close to him. 
 
 The winner of the Republican runoff will face Democratic nominee Doug Jones in the general election. 
 
 ___ 
 
 7:10 a.m. 
 
 Polls have opened in a special U.S. Senate election in Alabama where President Donald Trump is backing the establishment candidate to keep the seat once held by Attorney General Jeff Sessions. 
 
 Trump supported Sen. Luther Strange with a Tweet sent before voting began Tuesday morning. 
 
 Strange is being opposed by former Alabama Chief Justice Roy Moore, known for publicly displaying the Ten Commandments and opposing gay marriage. Former Trump aide Steve Bannon spoke at a rally in support of Moore on Monday night. 
 
 Moore led Strange by about 25,000 votes in the crowded August primary. Runoff polls have shown him leading, or in a dead heat with, Strange, who is a former state attorney general. 
 
 ___ 
 
 6 a.m. 
 
 President Donald Trump is making a final push for Sen. Luther Strange in Alabama's GOP primary. 
 
 Trump tweeted early Tuesday before voting began: "Luther Strange has been shooting up in the Alabama polls since my endorsement. Finish the job - vote for 'Big Luther.'" 
 
 The Alabama primary is being closely watched to see how much political sway Trump still has in the populist, conservative movement that helped send him to the White House. 
 
 Strange, the establishment-backed incumbent, is locked in a tight race with former Alabama Chief Justice Roy Moore. Moore is a jurist known for pushing unsuccessfully for the public display of the Ten Commandments and opposing gay marriage. He is backed by some of Trump's most ardent supporters and has the support of Trump's former aide Steve Bannon. 
 
 ___ 
 
 4:30 a.m. 
 
 U.S. Sen. Luther Strange and firebrand jurist Roy Moore face off in Alabama's GOP primary that has pitted President Donald Trump against a former top adviser. 
 
 Vice President Mike Pence campaigned for Strange in Alabama ahead of Tuesday's runoff. Trump's former strategist Steve Bannon endorsed Moore, arguing he's a better fit for the "populist, nationalist, conservative movement." 
 
 The two Republicans are vying for Attorney General Jeff Sessions' former Senate seat. The winner will face Democrat Doug Jones in December. 
 
 Strange, the state's former attorney general, was appointed to the seat in February. Moore is the state's former chief justice. He was twice ousted from those duties over stands against gay marriage and for the public display of the Ten Commandments.
– The fight for the Alabama Senate seat previously vacated by Attorney General Jeff Sessions looks poised to go to a Sept. 26 runoff election. But the path there officially kicks off Tuesday with a special election primary in which three candidates will be weeded down to two. President Trump and Mitch McConnell are backing former Alabama Attorney General Luther Strange, who was temporarily appointed to the seat after Sessions left it. But it's former Alabama Chief Justice Roy Moore who's the apparent front-runner, with Strange and US Rep. Mo Brooks trailing behind, reports Politico. More: A candidate needs 50% of the vote to take the seat, which most news outlets agree is unlikely to happen. Moore leads in some polls at around 35% support, with Strange and Brooks in a close race for second. Should Trump's favorite be eliminated, it "will call into question the influence of Trump's support in a reliably Republican state," per Politico. Not that Trump should be too disappointed with Brooks or Moore. Both are "Trumpian candidates," reports Axios. McConnell has a huge interest in the race, though. He and his allies have invested millions in Strange's campaign. Also key: Brooks has said he wants McConnell "fired." Not helping Brooks, however, is a controversial campaign ad he aired that included audio from the shooting of Steve Scalise, reports NBC News. Strange is likewise plagued by his appointment by former Gov. Robert Bentley in what some suspect was "a corrupt bargain to end the state's criminal investigation of Bentley," the New Republic previously reported. Reuters mentions the candidates' stances on issues like gay marriage and illegal immigration. The winner of the runoff election is likely to face one of two Democrats in December: either former US Attorney Doug Jones, backed by Joe Biden, or Robert Kennedy Jr., a Navy veteran with no relation to the famous Kennedy family, per Politico. Either way, the Republican winner will be sitting pretty. Alabama hasn't elected a Democrat to the Senate since 1992, per the New York Times. Polls close at 8pm EDT.