(ART ADV: With photos XNYT20, 99.). (With: FLA-TRUMP, OHIO-KASICH, TRUMP-SECURITY). Reporting was contributed by Jeremy W. Peters in Largo, Fla.; Yamiche Alcindor in Affton, Mo.; Amy Chozick in Cleveland; Thomas Kaplan in Strongsville, Ohio; Matt Flegenheimer in St. Louis; Jonathan Martin in Washington and Mitch Smith in Bloomington, Ill.
WEST CHESTER, Ohio — Unsettled by images of violence and ugliness at Donald Trump's rallies, the Republican leaders pushing to halt him are desperately targeting voters in the five big states that vote Tuesday.
The weekend of disturbances at Trump's rallies injected more unease into the race, and Trump's rivals' appeals turned emotional and urgent. On Sunday, Sen. Marco Rubio of Florida warned that a Trump White House would exploit hatred and stir violence.
"Imagine what that means for the country," Rubio said. "Imagine the tone it sets for our culture."
Ohio has emerged as a critical contest, the one large state voting this week where Trump appeared vulnerable. A victory here by Gov. John Kasich would complicate Trump's attempt to gather a majority of delegates needed for the nomination.
On the Democratic side, Sen. Bernie Sanders hoped for a repeat of his stunning upset over Hillary Clinton last week in Michigan as he hopscotched the Midwest to push his central message that American workers have suffered too much under trade deals.
Although the 11 states that voted two weeks ago on Super Tuesday received much attention, the contests this week are potentially even more important. Some 424 delegates are up for grabs on the Republican side, and, for the first time, states can award all of their delegates to the winner of the popular vote.
With three polls in recent days showing Kasich with an edge over Trump in Ohio, whose 66 delegates will be awarded winner-take-all Tuesday, Trump made multiple stops in the state over the weekend and added a last-minute return visit Monday — canceling an appearance in Florida, where he has a strong lead.
Trump held two rallies Sunday that were mainly free of protesters' disturbances.
The unrest at Trump's rallies have made the race more tense; Trump blamed Sanders' supporters, who successfully shut down a Trump rally in Chicago on Friday, for fomenting problems. But the candidate has been sympathetic to his own supporters who have become violent: On Sunday, he said he would consider paying the legal costs for a man who was charged last week with assaulting a protester who was being escorted out of a rally in Fayetteville, North Carolina.
In West Chester, Ohio, on Sunday, Trump spoke on a raised platform surrounded by a cordon of uniformed and plainclothes officers.
If Kasich is defeated in Ohio, he has indicated he will exit the race. Rubio is likely to withdraw, too, if he loses his home state of Florida. That would leave Trump facing Sen. Ted Cruz of Florida in a head-to-head competition, and polls show Trump is weaker in that matchup than in a multi-candidate field.
Cruz, who has largely ignored Ohio and Florida, focused on the other three states voting Tuesday: Missouri, North Carolina and Illinois, where he planned to hold five events Monday. Cruz said he was "neck and neck" with Trump in the three states.
In the Democratic race, aides to Clinton predicted tight races in the Midwestern states, where economically struggling voters have gravitated to Sanders. They were optimistic about winning Florida and North Carolina, where black, Hispanic and older voters are expected to give Clinton a healthy edge in the race for delegates.
Sanders has linked Clinton, in speeches and a television ad, to Rahm Emanuel, the mayor of Chicago, whose record on policing and fights with public-sector unions are unpopular with progressive voters.
In Missouri on Sunday, Sanders told a crowd that he had "from day one, been a leader in opposition to these disastrous trade policies." He added, "Secretary Clinton has supported virtually all of them."
With Sanders' ads attacking her support of global trade deals, Clinton has emphasized her proposals to lift employment while criticizing the Vermont senator for being short on specific plans.
Speaking at a factory in Youngstown, Ohio, over the weekend, Clinton vowed to end steel-dumping practices by China and other nations that undermine the economy in the industrial Mahoning Valley.
"I have always been committed to bringing back manufacturing," she said. "And I'm the only candidate, on either side, who actually has a plan to do that."
With Ohio a perennial swing state in presidential elections, and its racially and economically diverse voters fiercely fought over, it was no surprise that candidates converged here in the final hours.
Trump attacked Kasich for his support of the Common Core education standards, for a private sector job at Lehman Bros., whose 2008 collapse Trump said "almost destroyed the world," and for supporting trade deals that he blamed for harming the manufacturing sector.
Kasich accused Trump of creating "a toxic atmosphere" and said the New York billionaire was on the verge of disqualifying himself to represent the party because of his divisive speech. The world's eyes are glued to the scenes of mayhem and discord Trump has created, Kasich said.
"Our enemies are going to take advantage of them," Kasich told voters near Cleveland. "Our friends are scratching their heads saying, what the heck is happening in America?"
Kasich, who boasted of bringing 400,000 jobs to Ohio and has been barnstorming factories and other businesses that opened under his watch, has marshaled nearly the entire elected Republican apparatus of Ohio.
Matt Borges, chairman of the state Republicans, warned that if Trump is the nominee, his divisiveness would cost Republicans the state in the general election.
"If we don't carry Ohio in the fall, we don't elect a Republican to the White House," he said.
Trump's rally here was in West Chester, the home town of John Boehner, the former U.S. House speaker who resigned last year out of frustration with the no-compromise wing of House Republicans. In a rare public appearance, Boehner endorsed Kasich at a county Republican dinner in West Chester on Saturday. The Trump rally Sunday, just a few miles away, was attended by many hundreds more people.
"Kasich's done a great job with Ohio," said Doug Mason, a concrete laborer, but he still planned to vote for Trump. "I think Trump will be John Kasich on steroids."
A town hall-style event for Trump nearby was most notable for his response to a man who said it was important "for a lot of veterans in Ohio" that Trump clarify a comment, made last year, that prisoners of war like Sen. John McCain were not heroes. "Oh no, no, no," Trump said. "They are real heroes."