(AP) -- Donald Trump won a decisive victory in Florida's primary Tuesday night, forcing home-state Sen. Marco Rubio to abandon the race for the Republican presidential nomination and narrowing the once-crowded GOP field to three candidates.

"Do not give in to the fear," Rubio said as he suspended his bid and tried to sound optimistic about his party's future. "Do not give in to the frustration."

The outcome in Florida strengthened Trump's chances to secure the Republican presidential nomination.

Trump also was hunting for a victory in Ohio, where rival John Kasich is governor, while the fourth contender, Texas Sen. Ted Cruz, is hoping to pick up enough delegates to help force a contested national GOP convention in July.

Florida and Ohio award the most delegates in voting Tuesday; Missouri, Illinois and North Carolina also weigh in.

Trump's plainspoken -- while controversial -- appeals have resonated across the country, leaving other candidates reeling for a strategy to topple the unconventional front-runner.

"He will fix everything that is wrong with the economy and immigration," said Alex Perri, a 59-year-old retired firefighter from Margate, Florida, who was campaigning for Trump in the parking lot of an Oakland Park voting place.

Trump's promise to impose tariffs on goods from countries that don't "play fair" has been particularly resonant with voters across the industrial Midwest.

"America is a big business, and he could make money for us," said William McMillen, 70, a part-time warehouse worker in Columbus, Ohio. The registered Democrat said he voted for Trump.

Even as Trump racks up more wins, questions have intensified about whether he is doing enough to stem violence at his raucous rallies.

Trump said Tuesday on ABC's "Good Morning America" that his record-setting crowds have had "very, very little difficultly."

The New York real estate mogul backed away from a suggestion that he might cover legal costs for a supporter who punched a protester in the face during a rally last week in North Carolina. He has blamed a larger recent clash in Chicago on Democratic protesters.

His Republican rivals and other GOP leaders insist Trump deserves some responsibility, while both Rubio and Kasich in recent days have refused to say whether they would support a Trump nomination.

In a clear reference to Trump, House Speaker Paul Ryan, the GOP's top elected leader, declared that all candidates have an obligation to do what they can to provide an atmosphere of harmony at campaign events and not incite violence.

For some voters, Trump's tone has been a turn-off.

Tom and Cathy Lewis cast their votes Tuesday for Kasich, who lives in their hometown of Westerville, Ohio. Beyond feeling a hometown connection to the Ohio governor, the couple said they were looking for a candidate with integrity and someone they can trust.

"We need to have a man who will speak against things that are wrong," Cathy Lewis said.

In recent weeks, Republicans who dislike Trump have banded to wage multimillion-dollar advertising campaigns against him. One political ad highlights Trump's statements that appear to encourage violence.

Overall, there are 358 pledged delegates at stake on the GOP side in these primaries. The delegates are awarded differently depending on the state, with the winner in Florida and Ohio taking all of them.

Trump picked up all 99 delegates in Florida and now has 568. Ted Cruz has 370 delegates, Marco Rubio has 163 and John Kasich has 63.

It takes 1,237 delegates to win the Republican nomination for president.

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Associated Press writers Steve Peoples in Washington, Terry Spencer in Margate, Florida, Andrew Welsh-Huggins in Columbus, Ohio, and Kathleen Ronayne in Westerville, Ohio, contributed to this report.