BORDEN, Ind. — As Ted Cruz and John Kasich defended their extraordinary new alliance on Monday as the party’s last, best chance to stop Donald Trump’s march to the nomination, the Republican front-runner lashed out at what he called collusion by desperate rivals.
The New York billionaire, who is expecting another big delegate haul as five states vote Tuesday, intensified his attacks on the GOP presidential nomination system.
‘‘If you collude in business, or if you collude in the stock market, they put you in jail,’’ Trump said as he campaigned in Warwick, R.I. ‘‘But in politics, because it’s a rigged system, because it’s a corrupt enterprise, in politics you’re allowed to collude.
‘‘It shows how pathetic they are,’’ he said of his Republican rivals.
Connecticut, Pennsylvania, Delaware, and Maryland will hold primaries Tuesday, along with Rhode Island.
Cruz and Kasich announced the terms of an unprecedented agreement late Sunday night to coordinate primary strategies in three of the 15 remaining primary states, as a way to maximize their chances of stopping Trump from getting an outright majority of delegates.
Kasich will step back in the May 3 Indiana contest to let Cruz bid without interference for voters who don’t like Trump. Cruz will do the same for Kasich in subsequent contests in Oregon and New Mexico.
The arrangement does not address Tuesday’s primaries, where Trump is expected to add to his already hefty delegate lead.
Yet the shift offers increasingly desperate Trump foes a glimmer of hope in their long and frustrating fight to keep him from amassing enough delegates to seal his nomination and avoid a contested national convention in July.
Ignoring the Northeast on Monday, Cruz insisted, ‘‘We are at a fundamental fork in the road,’’ as he campaigned in Indiana.
‘‘It is big news today that John Kasich has decided to pull out of Indiana to give us a head-to-head contest with Donald Trump,’’ the Texas senator told reporters. ‘‘That is good for the men and women of Indiana. It’s good for the country to have a clear and direct choice.’’
The plan carries risks — especially as Trump bashes a ‘‘rigged’’ nomination system. Some would-be Cruz supporters in Indiana agreed with Trump’s criticism.
‘‘That’s kind of sneaky,’’ said Joe Conder, a 75-year-old retired civil engineer from Scottsville, Ind., who is deciding between Cruz and Trump. ‘‘It’s more about politics than getting things done.’’
Kasich sent mixed messages as he addressed the pact for the first time while campaigning in Philadelphia. Asked what Indiana voters should do next week, the Ohio governor urged them to vote for him.
‘‘I’ve never told them not to vote for me. They ought to vote for me,’’ Kasich said just 13 hours after promising to give Cruz ‘‘a clear path’’ in Indiana. He said he had simply agreed not to spend ‘‘resources’’ in Indiana.
Trump is the only Republican candidate who can clinch the GOP presidential nomination before his party’s national convention. Yet his path is narrow.
The front-runner needs to win at least four of the five Northeastern states on Tuesday. He enters the day with 845 delegates, 392 short of the 1,237 needed to represent his party in the general election in November.
Eliminated from reaching that total in the primaries, Cruz and Kasich can only hope to block Trump from reaching a majority — and a first-round convention victory — and thus force a contested convention where delegates could select a different nominee.
‘‘It is now abundantly clear that nobody is getting to 1,237,’’ Cruz declared on Monday. ‘‘We are headed to a contested convention. And at a contested convention, Donald Trump is in real trouble.’’
While in Rhode Island, Trump mercilessly mocked rival Kasich’s eating habits and calling him ‘‘stubborn’’ for remaining in the race.
‘‘I have never seen a human being eat in such a disgusting fashion,’’ Trump said.
He continued: ‘‘This guy takes a pancake and he’s shoving it in his mouth.’’ That’s not presidential, Trump added.
Trump was referring to Kasich’s morning conversation with reporters while eating. Trump said he had been watching television with his youngest son Barron when Barron told his father, “Daddy, don’t look.’’ Trump has been trying to teach his son to always take, ‘‘Little bites, little bites.’’
Trump also called Kasich stubborn and compared him to a child for refusing to exit the race when he has no chance of winning without a contested convention. He also took aim at Cruz, saying: ‘‘When he’s under pressure, he’s like a basket case.’’
Trump will join Megyn Kelly on a Fox TV special for her first interview with him since the fallout from their encounter during a GOP presidential debate last summer.
The businessman will be a guest on ‘‘Megyn Kelly Presents,’’ a prime-time special airing May 17, the network said Monday.
In a statement, Kelly said she asked Trump for the interview when they had a private meeting earlier this month. She said she looks forward to a ‘‘fascinating exchange.’’
Kelly and Trump’s second debate go-around, in March, proved far milder than the initial Republican debate that aired on Fox News last August. In that telecast, Trump was angered by Kelly’s question about statements he had made about women and he later began criticizing her on Twitter.
Fox News criticized Trump for having a ‘‘sick obsession’’ about Kelly and engaging in conduct unbecoming of a presidential candidate.