The race for the Republican party's nomination for president was now pared down to three candidates (Donald Trump, Ted Cruz and John Kasich) and the final debate between the candidates was scheduled to take place on March 21 in Salt Lake City. But the debate was cancelled after Trump and Kasich withdrew from the event. Trump announced that he was giving the event a pass because in his opinion there had been enough debates. Kasich said that he would not attend a debate without Trump.
Concerns about the border, immigration, and national security were the subject of many speeches leading up to the March 22nd contests in Arizona, Utah and American Samoa. Earlier in the month, 2012 GOP nominee Mitt Romney had made news on March 3rd, when he gave a speech attacking Donald Trump. Romney had not endorsed anyone but was increasingly concerned about Trump's front-runner status. Prior to the speech, Romney publicly criticized Trump for not releasing his taxes, saying there might be a "bombshell" in them. Trump responded by calling Romney "one of the dumbest and worst candidates in the history of Republican politics."

Romney gave his speech on March 3, 2016, at the Hinckley Institute of Politics. In the speech he criticized Trump's personal behavior, his business performance, and his domestic and foreign policy stances. He called Trump "a phony, a fraud" and said that Trump was "playing members of the American public for suckers", adding that "If we Republicans choose Donald Trump as our nominee, the prospects for a safe and prosperous future are greatly diminished."
In response Trump called Romney a "choke artist". Romney did not endorse any particular candidate, but he encouraged Republicans to engage in tactical voting, by supporting whichever of the remaining rivals had the best chance to beat Trump in any given state. Romney announced that he was voting for, although not endorsing, Ted Cruz for president prior to the March 22 Utah caucus.
It was the subject of debate whether Romney's pronouncement helped or hurt Trump. In Utah however Cruz won over 50% of the popular vote, meaning that he won all 40 of the state's delegates. Cruz received 122,563 votes (69.17%), Kasich finished second with 29,779 votes (16.81%) and Trump finished third with 24,861 votes (14.03%).
Trump won all 58 delegates in winner-take-all Arizona Primary with 286,743 votes (45.95%). Cruz finished second with 172,294 votes (27.61%). Both Trump and Cruz will receive at least one of American Samoa's nine delegates, but the remaining delegates in that caucus are uncommitted. American Samoa and Utah were the last caucuses of the 2016 primary season.
As a Trump nomination appeared more likely, those in the Stop Trump movement, such as the Club for Growth, continued their efforts as the Wisconsin primary approached. Trump said that he foresaw the outbreak of riots if he were denied the nomination at the convention. Cruz began picking up endorsements of establishment figures dismayed by the prospect of a Trump nomination, including that of Mitt Romney just before the March 22 Utah vote.
The Democrats
Following the March 15 primaries, the Democratic Party race moved to a series of states that were considered to be more favorable for Sanders and in which he was polling stronger. Arizona, Idaho, and Utah held primaries on March 22, a day called "Western Tuesday" by some in the media.
Sanders made efforts to close the gap in Arizona after his surprise win in Michigan, but these efforts were too little, too late. Clinton won the primary, receiving 262,459 votes (56.29%), gaining 47 delegates in the process (42 pledged, and 5 unpledged). Sanders received 192,962 votes (41.39%) and 35 delegates (33 pledged and 2 unpledged). Controversy arose out of the primary when some accused the state of voter suppression. The Arizona state administration had reduced election spending by 70 percent, reducing the number of polling places from 200 to 60 in the state's most populous county and causing long lines for voters on election day.
Sanders won big in Idaho and Utah. In Idaho he received 18,640 votes (78.04%) to win 20 delegates (18 pledged and 2 unpledged). Clinton finished second with 5,065 votes (21.21%) for 6 delegates (5 pledged and 1 unpledged). In Utah Sanders received 61,975 votes (79.26%) to win 27 pledged delegates, and Clinton received 15,855 votes (20.28%) to win 8 delegates (6 pledged and 2 unpledged). The victories allowed Sanders to close his delegate deficit by 25. On Monday, March 21, the results of the Democrats Abroad primary were announced. Sanders was victorious and picked up nine delegates to Clinton's four.

Sanders was on a roll that would continue during the following weekend's primaries. The question was whether his momentum swing would change the race or whether it had arrived too late.