In a brazen effort to thwart front-runner Donald Trump from winning the Republican presidential nomination, his two remaining rivals have agreed to a plan intended to force the party into a contested convention in July.
Texas Senator Ted Cruz and Ohio Governor John Kasich agreed not to campaign against each other in several of the remaining state primaries in a last-ditch effort to deny Mr. Trump the delegates he needs to win on the first ballot at the party's Cleveland convention in July. But the pact already appeared shaky on Monday, just hours after it was announced, with Mr. Cruz calling it "momentous" while Mr. Kasich said it was "no big deal."
The deal comes too late to have any impact on Tuesday's primaries in Pennsylvania, Connecticut, Delaware, Maryland and Rhode Island. Mr. Trump is expected to win all five.
Both Mr. Cruz and Mr. Kasich said they were co-operating to boost Republican chances of beating presumptive Democratic nominee Hillary Clinton in November's election, but an outraged Mr. Trump denounced them on Monday as "weak" and "pathetic" political failures colluding in a corrupt process to deny voters their choice.
"If you collude in business or if you collude in the stock market, they put you in jail," said Mr. Trump, the New York property magnate who has outraged and insulted many while building a massive lead among Republican primary voters. "In politics, because it's a rigged system, because it's a corrupt enterprise, in politics you're allowed to collude," he added.
Mr. Cruz, who has been accused by Mr. Trump of being ineligible to run for president because he was born in Canada, rejected the accusations of collusion. "I don't doubt that Donald Trump is going to scream and yell and curse and insult and probably cry and whine some as well," he said.
Mr. Kasich, who has largely stayed above the name-calling and insults that have turned the Republican primaries into an unseemly mess, dismissed the brouhaha over the pact, which, in effect, cedes various states to the other, thereby allowing both candidates to concentrate on states were they have the best chance of damaging Mr. Trump. Mr. Kasich will spend no money or time in the May 3 primary in Indiana, where Mr. Cruz is stronger, while Mr. Cruz will defer to Mr. Kasich in Oregon and New Mexico, which vote on May 17 and June 7, respectively.
"So what? What's the big deal?" Mr. Kasich said. "I'm not over there campaigning and spending resources."
The pact, unprecedented since the 1970s, is just the latest twist in the Republican roller-coaster ride this cycle.
Larry Sabato, director of the University of Virginia's Center for Politics, suggested Mr. Cruz and Mr. Kasich were driven in desperation to the deal after Mr. Trump swept nearly all of New York State's 95 delegates last week. "They know he's going to have a great night tomorrow," Mr. Sabato said, referring to the five northeastern states voting on Tuesday. "If things are not shaken up, Trump's going to be the nominee. They have to do something big to shake things up. They're hoping that this is it. Maybe it is, maybe it isn't."
Mr. Trump, who has repeatedly threatened to launch an independent bid for the White House if he feels unfairly treated by the Republican National Committee, was even angrier than usual. "This horrible act of desperation, from two campaigns who have totally failed, makes me even more determined, for the good of the Republican Party and our country, to prevail," he said.
The non-compete pact so far applies only to three of the remaining 15 states, but it could be expanded if the "Stop Trump" effort, backed by big Republican donors and many senior party officials, grows. Although Mr. Trump has a huge lead in delegates, more than six in 10 voters in Republican primaries to date backed his rivals.
Democrats are also voting on Tuesday, and former first lady Ms. Clinton, already the presumptive presidential candidate with a commanding lead over Vermont Senator Bernie Sanders, is expected to extend it.
On Monday, she was hammering away at Mr. Trump and ignoring Mr. Sanders.
"If you want to be president of the United States, you've got to get familiar with the United States," Ms. Clinton said. "Don't just fly that big jet in and land it and go make a big speech and insult everybody you can think of."
Mr. Sanders, with his avuncular style and impassioned calls to break up big Wall Street banks, provide a free university education for everyone and reduce the widening wealth gap, has delivered a powerful message, especially among young people. He insists he will campaign all the way to the Democratic convention in Philadelphia. But if he loses all five states, as expected, on Tuesday, he may cease skewering Ms. Clinton on her most vulnerable weaknesses: integrity and seemingly being beholden to big money.