McSally was expected to run as the establishment candidate in the Republican primary, where her opponents included former State Senator Kelli Ward and former Maricopa County Sheriff Joe Arpaio. McSally, a strong fundraiser, was the preferred candidate of national Republicans and Arizona Governor Doug Ducey. McSally's history of criticizing President Donald Trump drew rebuke from conservative groups including the Club for Growth, the Senate Conservatives Fund, and FreedomWorks. McSally had previously distanced herself from Trump, choosing not to endorse him in 2016 and calling his comments about sexual assault "disgusting" and "unacceptable." But in the lead-up to announcing her candidacy for Senate, McSally began to embrace Trump, running ads echoing his conservative immigration policy positions. "Politico" wrote: "Martha McSally wants to make one thing clear before she launches an Arizona Senate campaign: She's a big fan of President Donald Trump."