(Newser) – Republican leaders trying to stop Donald Trump from winning the nomination might run out of time on Tuesday, when voters in five states—including winner-take-all states Ohio and Florida—could put the tycoon on an almost unblockable path to the nomination. With a total of 367 delegates at stake, delegates will be awarded proportionately in North Carolina, while Missouri awards delegates by district and Illinois uses a similar system. A roundup of coverage:

The New York Times looks at the role of Ohio, which is likely to be crucial to both the Republican and Democratic contests. The state GOP is firmly behind Gov. John Kasich, who is in a tight race with Trump and has said he will end his campaign if he doesn't carry the state.

CNN reports that anti-Trump groups, including a PAC led by Jeb Bush staffers, are hitting him hard with attack ads. One cable ad features women reading Trump insults like "bimbo" and "fat pig."

FiveThirtyEight crunches the numbers and finds that Kasich is the favorite to win Ohio, while Trump is the favorite in other states, including Florida, where Marco Rubio is given just a 4% chance of winning his home state—and of having a reason to continue his campaign.

The Wall Street Journal was present for some last-minute campaigning in which Trump spoke of knockout wins. "If we win Ohio and if we win Florida, then everybody agrees, every one of these guys, that it's pretty much over," he told supporters at a rally in Tampa at which he was joined by Sarah Palin, who denounced the "petty, punk-ass little thuggery" of Trump protesters.

Ted Cruz, meanwhile, was reaching out to Kasich and Rubio supporters in the belief that it will be a two-man race between him and Trump by Wednesday. Politico looks at the senator's state-by-state plan.

The Washington Post looks at whether the "political free-for-all of an old-school contested convention" is a real possibility this year.

Ben Carson, who has endorsed Trump, warned against a contested convention Monday night, saying a fractured GOP would be sure to lose both the presidency and the Senate if that happens, the Hill reports. He said that even if Trump turned out to be a terrible president, "we're only looking at four years."

(Read more Election 2016 stories.)