Republican presidential front-runner Mitt Romney cruised to victory in the Nevada caucuses Saturday night, notching a second straight triumph over a field of rivals suddenly struggling to keep pace. 
 
 Republican presidential candidate former Massachusetts Gov. Mitt Romney greets supporters at his Nevada caucus night victory celebration in Las Vegas, Saturday, Feb. 4, 2012. (AP Photo/Julie Jacobson) (Associated Press) 
 
 Republican presidential candidate former Massachusetts Gov. Mitt Romney greets supporters at his Nevada caucus night victory celebration in Las Vegas, Saturday, Feb. 4, 2012. (AP Photo/Gerald Herbert) (Associated Press) 
 
 Republican presidential candidate, former Massachusetts Gov. Mitt Romney, greets supporters after speaking at a campaign rally in Colorado Springs, Colo., Saturday, Feb. 4, 2012. (AP Photo/Gerald Herbert) (Associated Press) 
 
 Republican presidential candidate, former House Speaker Newt Gingrich speaks during a campaign stop at the International Church of Las Vegas on Friday, Feb. 3, 2012 in Las Vegas, Nev. (AP Photo/Evan... (Associated Press) 
 
 Republican presidential candidate Rep. Ron Paul, R-Texas, speaks during a campaign stop at Bethel University Saturday, Feb. 4, 2012, in Arden Hills, Minn. (AP Photo/Charles Rex Arbogast) (Associated Press) 
 
 The caucuses drew little attention in the nominating campaign, but Nevada figures to be a fierce battleground in November between the winner of the Republican nomination and Democrat President Barack Obama. The state's unemployment rate was measured at 12.6 percent in December, the worst in the U.S. 
 
 Romney unleashed a sharp attack on Obama, whose economic policies he said have "made these tough times last longer." 
 
 "President Obama seems to believe America's role as leader in the world is a thing of the past. I believe the 21st century will be and must be an American century," Romney said to cheers from his backers. 
 
 Romney, the former Massachusetts governor, held a double-digit lead over his nearest pursuer as the totals mounted in a state where fellow Mormons accounted for roughly a quarter of all caucus-goers. 
 
 Former House of Representatives Speaker Newt Gingrich and Texas Rep. Ron Paul vied for a distant second. Former Pennsylvania Sen. Rick Santorum trailed the field. Returns from 14 of 17 counties showed Romney with 42 percent support, Gingrich with 25 percent, Paul with 20 percent and Santorum with 13 percent. 
 
 Yet to report its results was Clark County, which includes Las Vegas and often accounts for half or more of the votes in a statewide election. 
 
 Romney's victory capped a week that began with his double-digit win in the Florida primary. That contest was as intense as Nevada's caucuses were sedate _ so quiet that they produced little television advertising, no candidate debates and only a modest investment of time by the contenders. 
 
 According to the AP count, Romney began the day with 87 of the 1,144 delegates needed to win the Republican nomination. Gingrich had 26, Santorum 14 and Paul 4. 
 
 Preliminary results of a poll of Nevada Republicans entering their caucuses showed that nearly half said the most important consideration in their decision was a candidate's ability to defeat Obama this fall, a finding in line with other states. 
 
 About one-quarter of those surveyed said they are Mormon, roughly the same as in 2008, when Romney won with more than a majority of the vote in a multi-candidate field. 
 
 The entrance poll was conducted by Edison Research for The Associated Press at 25 randomly selected caucus sites. It included 1,553 interviews and had a margin of sampling error of plus or minus 4 percentage points. 
 
 A total of 28 delegates were at stake in the state-by-state race to lock up the 1,144 needed to secure the Republican nomination. 
 
 Nevada awarded its delegates in proportion to the caucus vote totals, meaning that any candidate who captured at least 3.57 percent of the total number of ballots cast would be rewarded. By contrast, Romney's victory in the Florida primary on Tuesday netted him all 50 of the delegates at stake there. 
 
 From Nevada, the calendar turns to caucuses in Minnesota and Colorado and a non-binding primary in Missouri on Tuesday. 
 
 Maine caucuses end next Saturday, and the next seriously contested states are expected to be primaries in Michigan and Arizona on Feb. 28. 
 
 Nevada caucuses, coming four days after the Florida primary, meant little time for the type of intense campaign that characterized the first month of the race. 
 
 The most memorable event of the four-day Nevada campaign was an endorsement that flamboyant billionaire Donald Trump bestowed on Romney in Las Vegas in a circus-like atmosphere that followed reports he would back Gingrich. 
 
 By the time Nevada Republicans caucused, Paul was campaigning in Minnesota, Santorum in Colorado. 
 
 Eager to demonstrate he intends to fight on, Gingrich announced plans to campaign next week in Ohio, one of several states with a primary on March 6. 
 
 His Florida victory in hand, Romney was acting like a front-runner again, campaigning against Obama more than Gingrich. Restore Our Future took on the former speaker, airing ads that said he consistently overstated his connections to Ronald Reagan. ||||| Colorado, Minnesota and Missouri all hold contests Tuesday, making it the first day of the 2012 campaign that multiple states deliver a verdict. 
 
 While Mitt Romney appears to be in solid shape in Colorado, Rick Santorum is gathering momentum in the latter two states and could deliver a surprisingly strong performance. Newt Gingrich, meanwhile, isn’t poised to have a good day: Recent polling has him running third in Colorado and Minnesota, and he’s not even on the ballot in Missouri. 
 
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 As for Ron Paul, the Colorado and Minnesota caucuses offer an opportunity to rebound after under-performing in Nevada on Saturday. 
 
 Below are POLITICO’s five things to watch in Tuesday’s contests: 
 
 1) Santorum’s opening 
 
 If Santorum is ever going to offer a compelling case for staying in the race, the time to do it is Tuesday. He has a shot at winning two states, Minnesota and Missouri, which would provide a jolt of momentum at a time when Gingrich is flagging. 
 
 The deeply conservative Minnesota GOP — with its high percentage of evangelicals and social conservatives, it’s more like Iowa than Florida or New Hampshire — is built for a candidate like Santorum. While Romney won the caucuses easily in 2008, back then he was the more conservative alternative to McCain, whom he defeated by a nearly 2-to-1 margin. This time around, according to recent Public Policy Polling surveys, Santorum has the edge over Romney, with Gingrich and Ron Paul battling for third. 
 
 Just read between the lines of former Minnesota Gov. Tim Pawlenty’s Romney campaign press call Monday. Pawlenty declined to predict a winner, noted that Minnesota caucus-goers tend to “gravitate toward the perceived most conservative candidate,” and talked about the “different dynamics” of his home state. The fact that the Romney camp decided to hold a call pegged to Santorum was revealing in itself. 
 
 Missouri also figures to be favorable terrain, which is why Santorum will begin his Tuesday in Colorado but finish in Missouri, where he’ll hold his primary night party in St. Charles. 
 
 There’s no reason that Santorum can’t win there. Gingrich isn’t a factor and Romney and Paul haven’t paid the state much attention. And the former Pennsylvania senator’s message should have great appeal to Republicans in a state with a high percentage of evangelicals. 
 
 Missouri’s election is nothing more than a beauty contest, with no delegates up for grabs. But the stakes are still very high for Santorum. If he emerges as the victor in two races, on Wednesday he can point to three victories in the eight states that have voted so far — that’s two more wins than Gingrich. 
 
 If Santorum fails to win any state Tuesday, it’s a very different story, because if he can’t win in Missouri, where he has a clean shot at Romney and his rivals have mailed it in, where can he win? 
 
 2) Romney’s Colorado performance 
 
 Romney won big in Colorado in 2008, and it’s the state he’s best positioned to capture Tuesday. If he can’t win there, it could be a rough night for him. 
 
 The former Massachusetts governor has a solid organization in Colorado, deep and wide establishment support and a healthy lead in the polls. Romney losses in Minnesota and Missouri can be easily explained away. Not Colorado. ||||| DENVER—Rick Santorum jolted the Republican presidential race Tuesday with a three-state sweep of nominating contests in Colorado, Missouri and Minnesota, puncturing Mitt Romney's claim to be the unstoppable front-runner. 
 
 Rick Santorum jolted the Republican presidential race Tuesday with a three-state sweep of contests in Colorado, Missouri and Minnesota, puncturing Mitt Romney's claim to be the unstoppable front-runner. Patrick O'Connor has details on Lunch Break. 
 
 Mr. Santorum's victories—one in the Mountain West and two in the Midwest—gave his campaign a much-needed burst of momentum while stirring doubt about Mr. Romney's abilities to woo conservatives to his side in important electoral swing states such as Missouri and Colorado. So far, Mr. Romney has won in states where he has devoted significant campaign time and advertising dollars. 
 
 In two of the states, Colorado and Minnesota, Mr. Romney had won by large margins in 2008. He was hugely favored in Colorado in the days leading up to the Tuesday caucus. Two of his top aides have deep experience in the state, and his campaign has been busy organizing there for months. 
 
 Mr. Santorum on Wednesday morning said the trio of wins had attracted donors. "I think last night we raised a quarter of a million dollars online," he said on CNN's "Starting Point with Soledad O'Brien." "So we're doing really well and we feel like going forward we're going to have the money we need to make the case we want to make." 
 
 On MSNBC's "Morning Joe," Mr. Santorum said he's looking forward to the Michigan contest on Feb. 28 and the rush of primaries afterward. Ten states hold contests on Super Tuesday, March 6. 
 
 He said Michigan—where Mr. Romney grew up and his father, George Romney, was governor—"is a great place for us to plant our flag and talk about jobs and manufacturing and giving opportunities for everybody in America to rise." 
 
 Rick Santorum got a big boost to his campaign on Tuesday when he defeated his GOP rivals in primary elections in Missouri, Minnesota and Colorado. Watch Santorum speak to supporters at his primary night rally in St. Charles, Missouri. (Photo: Getty Images) 
 
 Of the eight nominating contests so far, Mr. Santorum has now won four, while Mr. Romney has won three and Newt Gingrich one—a tally that seemed unlikely only a few days ago. Until Tuesday, Mr. Santorum, a former Pennsylvania senator, had won only a single contest, a narrow victory in Iowa's Jan. 3 caucuses. 
 
 In Missouri's primary, Mr. Santorum won 55% of the vote, while Mr. Romney followed with 25%. Texas Rep. Ron Paul was trailing with 12%. Mr. Gingrich wasn't on the Missouri ballot. 
 
 Enlarge Image Close Associated Press Rick Santorum spoke in Colorado Springs, Colo., today. 
 
 Mr. Santorum's Missouri victory margin was substantial: He won 75,000 more votes than Mr. Romney and 29,000 more than Mr. Romney's combined Iowa and Nevada totals. 
 
 While the Tuesday results didn't directly award any of the delegates needed to claim the GOP nomination, they showed voters rejecting Mr. Romney even in states where he had performed well four years ago. 
 
 Mr. Romney had carried Minnesota's caucuses in 2008 but placed third there on Tuesday. With 98% of the vote counted, Mr. Santorum had 45% of the vote, while Mr. Paul had 27%. Mr. Romney had 17% and Mr. Gingrich 11%. 
 
 Republicans Vie for Support View Slideshow Evan Vucci/Associated Press Former Speaker of the House Newt Gingrich met with voters during a campaign stop at the Price Hill Chili Restaurant in Cincinnati, Ohio, Tuesday. 
 
 Poll Tracker WSJ's guide to the latest political polls On the Issues Read where each Republican hopeful stands on major issues in the campaign. View Interactive More photos and interactive graphics 
 
 With all Colorado precincts counted, Mr. Santorum had 40%, to 35% for Mr. Romney. Four years ago, Mr. Romney carried Colorado's caucuses with 60% of the vote. 
 
 Mr. Santorum has lagged in the primaries held since his Iowa win in early January. His three-state sweep Tuesday will buttress his argument that he, not Mr. Gingrich, is the GOP's top alternative to Mr. Romney. The victories also will likely give a fund-raising boost to Mr. Santorum, who has kept his campaign running on a shoestring budget since launching his bid last summer. 
 
 "Conservatism is alive and well in Missouri and Minnesota," Mr. Santorum said at a victory rally in St. Charles, Mo. "I don't stand here to be the conservative alternative to Mitt Romney," he said, prompting loud chants of support. "I stand here to be the conservative alternative to Barack Obama." 
 
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 Mr. Romney told followers in Denver that the Colorado race was "too close to call" but that he expected to come in either first or second. "I expect to become the nominee, with your help," he said. 
 
 Mr. Romney still has far greater financial and organizational resources than do his opponents, advantages in what could be a long, state-by-state fight for convention delegates. 
 
 "We had to make tough choices. We're very focused on the delegates," said Stuart Stevens, the campaign's chief strategist. "There will be the same amount of delegates today as there are tomorrow." 
 
 As for Minnesota, Mr. Stevens suggested that Mr. Romney fell victim to the same forces that brought down Sen. John McCain in the state in 2008, allowing Mr. Romney to seal a victory there four years ago. 
 
 "Last time I think that we were benefiting from being someone who was seen as a conservative alternative to someone who was leading the race at the time," Mr. Stevens said. "Rick Santorum spent a lot of time there to his credit and really worked it." 
 
 WSJ's Patrick O'Connor has details of Rick Santorum's trio of victories in Minnesota, Colorado and Missouri. AP Photo/Jeff Roberson 
 
 Anticipating defeat in at least one and possibly two of Tuesday's contests, the Romney campaign had sought early in the day to play down their significance, noting that none of them would result directly in the awarding of delegates. 
 
 Minnesota and Colorado held nonbinding caucuses. The Missouri primary had no delegates at stake. After Tuesday's flurry of votes, the candidates face a three-week lull that will test their endurance and cash reserves ahead of Super Tuesday. 
 
 In a sign of how the race was leaping toward that showdown, Mr. Gingrich spent most of Tuesday campaigning in Ohio, a Super Tuesday state, while Mr. Romney planned to fly Wednesday to Georgia, which also votes that day. 
 
 Some top conservatives are predicting the nomination brawl could extend well into the spring if Mr. Romney isn't able to deliver a knockout blow on Super Tuesday. 
 
 "That will be very tough for the party if millions of dollars more are spent on Republicans attacking Republicans," said Al Cardenas, president of the Conservative Political Action Committee, which is hosting its annual conference this week. 
 
 A memo released Tuesday by Mr. Romney's political director, Rich Beeson, asserted that the former Massachusetts governor's larger organization and cash reserves offered little chance for his rivals to catch up in the weeks and months ahead. 
 
 The Romney camp has already shifted its sights to the next contests, in Arizona and Michigan on Feb. 28, states where the former governor appears to be favored. Mr. Romney won Michigan and placed second in Arizona in 2008. 
 
 Romney advisers say the candidate will spend much of the next three weeks raising money to fuel what most expect to be the priciest month of the campaign. Advertising simultaneously in big Super Tuesday states such as Georgia, Tennessee, Massachusetts and Ohio could cost the Romney campaign tens of millions of dollars. 
 
 Mr. Gingrich is counting on making strong March performances in the South, although he is also making a play for Ohio. But the former speaker will have to wait two weeks until the candidates meet for another televised debate, forums that have boosted him at times. 
 
 —Patrick O'Connor contributed to this article. 
 
 Write to Neil King Jr. at neil.king@wsj.com and Danny Yadron at danny.yadron@wsj.com 
 
 Corrections & Amplifications 
 
 Rick Santorum was a former Pennsylvania senator. An earlier version of this article incorrectly said he was a former governor.
– The polls this week were right: Mitt Romney easily won the Nevada caucuses tonight, just as he did four years ago, report the AP and CNN. That's two straight victories for the frontrunner. The more interesting battle was that for second place: Romney took 42%, but Ron Paul at times looked poised to trounce Newt Gingrich. Gingrich prevailed in the final tally with 25%, Paul with 18%, and Rick Santorum had 13%. As he did after his South Carolina win, Romney addressed supporters and put the focus on the White House rather than his rivals."President Obama seems to believe America's role as leader in the world is a thing of the past," he said. "I believe the 21st century will be and must be an American century." Next up after tonight: Tuesday night caucuses in Minnesota and Colorado, and a primary in Missouri. (No delegates will be awarded in the Missouri contest, and Gingrich isn't even on the ballot, notes the Washington Post.)