By John Whitesides
WASHINGTON (Reuters) - Front-runner Donald Trump looks to take another step toward winning the Republican presidential nomination in contests in Arizona and Utah on Tuesday, aiming to deal another setback to the party establishment's flagging stop-Trump movement.
The billionaire businessman has rolled up a big lead in convention delegates who will pick the Republican nominee, defying weeks of attacks from members of the party establishment worried he will lead the Republicans to defeat in the Nov. 8 presidential election.
In Arizona, which is one of the U.S. states that borders Mexico, Trump's hardline immigration message is popular and he leads in polls, while in Utah Trump lags in polls behind top rival Ted Cruz, a U.S. senator from Texas.
Arizona will award its entire slate of 58 delegates to the winner of Tuesday's primary. In Utah, the state's 40 delegates will be awarded proportionate to the popular vote, unless a single candidate captures at least 50 percent of the vote, in which case that person will be awarded all the delegates.
On Monday, Trump tried to rally worried party leaders to his insurgent candidacy during a stop in Washington, D.C., where he warned against efforts to deny him the nomination if he falls short of securing the 1,237 delegates needed ahead of the party's July convention. Trump now has 678 delegates.
"I think it is going to be very hard for them to do," Trump said on CNN of any effort to deny him the nomination if he falls short. "I have millions of votes more than anybody."
Democrats also will vote on Tuesday, in Arizona, Utah and Idaho, with front-runner Hillary Clinton aiming to pile up more delegates in her race against challenger Bernie Sanders.
Sanders, a U.S. senator from Vermont, is looking for wins in many of the six Democratic contests this week. Alaska, Hawaii and Washington will vote on Saturday. But because Democratic delegates are awarded proportionally in all states, Clinton will keep adding to her delegate total even if she is not the winner in a given state.
Tuesday's Republican contests are the first since U.S. Senator Marco Rubio of Florida dropped out. Ohio Governor John Kasich is still in the race, splitting the anti-Trump vote with Cruz.
"We welcome Marco's supporters with open arms," Cruz said on CNN, saying a Trump candidacy in November would be "a disaster" that would ensure a Clinton win.
In Arizona, Trump has the backing of former Republican Governor Jan Brewer and Maricopa County Sheriff Joe Arpaio, two of the most prominent supporters of a crackdown on illegal immigrants.
In Utah, Mitt Romney, the 2012 Republican presidential nominee, has said he will vote for Cruz.
Romney recorded phone messages on behalf of Cruz, saying, "He is the only Republican candidate who can defeat Donald Trump" and that a vote for Kasich was equivalent to a vote for Trump.
(Editing by Leslie Adler)