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Republican primary front-runner Donald Trump is setting his sights on Ohio as polls show him trading the lead with John Kasich in the governor's home state, upping the already intense pressure on the underdog candidate to pull off a big win Tuesday -- or pack it in.

Trump shook up his campaign schedule to hold a rally outside Youngstown, Ohio, Monday evening. He originally had planned to be in Florida at that time, but cancelled the rally in order to schedule the stop in Ohio.

Trump clearly is feeling bullish about his chances in both states, with polls already showing him leading Florida Sen. Marco Rubio in the Sunshine State by double-digits.

"If we win Ohio and Florida, we can go attack Hillary ... It's pretty much over," Trump said at a town hall in Tampa, Fla., earlier Monday.

To schedule the Ohio event, the Trump campaign said it was postponing an evening event at Trump National Doral in Miami. “If we are successful on Election Day, we will do a celebration in Doral after the election,” the campaign said.

For Kasich, who has yet to win a primary or caucus this year, Tuesday is do or die.

He has vowed to win his home state, and has effectively staked his survival in the race on doing so. Even before Tuesday's primaries -- when Ohio and four other states will vote -- Kasich saw warning signs about his numbers in the Midwest when Texas Sen. Ted Cruz bested him for second place in next-door Michigan.

“You’ve got to win your home state,” Basil Smikle Jr., executive director of the New York State Democratic Party, told FoxNews.com’s Strategy Room.

Kasich, though, who still leads Trump slightly in an average of Ohio polls, is vowing to come away the victor Tuesday night.

“I am going to win Ohio, and it’s going to be a whole new ballgame,” Kasich said Monday on Fox News.

While it would seem virtually impossible for Kasich, who is in last place in the delegate count, to catch up to Trump or even Cruz, Kasich maintains that nobody will have enough delegates to secure the nomination by the July convention. His goal is to keep it open.

“I don’t think anybody at this pace is going to have enough delegates to win,” Kasich said Monday.

On “Fox News Sunday,” Kasich said not only was he doing well in Ohio but also “doing well in other states.”

“We’re going to be very competitive, “he said.

Former GOP presidential candidate Mitt Romney also hit the campaign trail for Kasich twice in Ohio on Monday. He’s also made robocalls for other candidates in an effort to deny Trump the nomination.

A recent NBC/Marist survey shows Kasich holding the edge with 39 percent to Trump’s 33 percent. Cruz has 19 percent while Rubio has just 6 percent.

Kasich, though, said last month that if he does not win his home state, he'll drop out.

Trump, for his part, sees an opportunity to at least clear away half the remaining field, with wins in Ohio and Florida, which both hold winner-take-all primaries. He wants to foreclose the possibility of an open convention in July.

Tuesday’s primaries in Ohio and Florida are among five high-stakes, must-wins for both Kasich and Rubio, respectively. Both trail Trump and Cruz in the delegate count.

“If Trump wins Florida – which it looks like he is going to do – and Ohio, he is well on his way to winning the nomination on pure numbers,” Liz Peek, a columnist at The Fiscal Times, told FoxNews.com’s Strategy Room.

She added, “If Kasich could stop him in Ohio, then all the other states tomorrow night and others to follow are proportional, so he probably won’t get to the magic number that he needs for the nomination.”

For Trump, things are looking sunnier in Florida.

According to new Quinnipiac University polls, the New Yorker is up double-digits against Rubio. Of likely Republican voters, 46 percent support Trump compared to 22 percent for Rubio.

Cruz comes in third with 14 percent, while Kasich finishes fourth at 10 percent.