Ted Cruz and John Kasich issued near-simultaneous statements outlining an agreement that may be unprecedented in modern American politics. The Kasich campaign will give Cruz "a clear path in Indiana." In return, the Cruz campaign will "clear the path" for Kasich in Oregon and New Mexico.
"Having Donald Trump at the top of the ticket in November would be a sure disaster for Republicans," Cruz's campaign manager, Jeff Roe, said in a statement explaining the new plans. "Not only would Trump get blown out by Clinton or Sanders, but having him as our nominee would set the party back a generation."
Added Kasich's chief strategist, John Weaver, "Our goal is to have an open convention in Cleveland, where we are confident a candidate capable of uniting the party and winning in November will emerge as the nominee."
"Having Donald Trump at the top of the ticket in November would be a sure disaster for Republicans." —Jeff Roe, Cruz campaign manager
The arrangement marks a sharp reversal for Cruz's team, which aggressively opposed the idea of a co-ordinated anti-Trump effort as recently as late last week. Yet it underscores a bleak reality for the billionaire businessman's Republican foes: Time is running out to stop him.
The announcement came less than 48 hours before voting begins across five Northeastern states where the New York billionaire is poised to add to his already overwhelming delegate lead. Trump campaigned Sunday in Maryland, which will vote on Tuesday along with Rhode Island, Connecticut, Pennsylvania and Delaware.
Speaking to several thousand people in an airplane hangar in Hagerstown, Maryland, Sunday evening, Trump stressed repeatedly that he expects to win the 1,237 delegates needed in the first round of voting to stave off a contested convention.
"I only care about the first. We're not going for the second and third and fourth and fifth," said Trump.
Indiana a critical turning point
Even before the plan was announced, Cruz all but abandoned the Northeastern states in favour of Indiana, which holds its primary on May 3. Both Cruz and Kasich had cast the state as a critical turning point. Under the terms of the new agreement, however, Kasich will allow Cruz take on Trump without interference.
As recently as three days ago Kasich's campaign announced investments in Indiana, including the opening of two offices and the creation of a campaign leadership team. And he had planned to campaign there Tuesday, with a town hall and gathering in Indianapolis to watch the results of Tuesday's primaries.
Those events have been cancelled.
As Kasich backs out of Indiana, Cruz promised to not compete in primary contests in Oregon on May 17 and New Mexico on June 7.
Ted Cruz (L) listens to rival John Kasich speak at the U.S. Republican presidential candidates debate in Detroit, Michigan, March 3, 2016. (Photo: Reuters)
"We will focus our time and resources in New Mexico and Oregon, both areas that are structurally similar to the Northeast politically, where Gov. Kasich is performing well," Weaver said.
Like Cruz's campaign, Kasich's campaign encouraged allied super PACs and other outside groups to "honour the commitments."
Trump did not immediately respond to the agreement. He has repeatedly denounced the GOP's presidential nominating system as "rigged."
Sanders looking for momentum in New England
There was far less drama on the Democratic side Sunday.
Underdog Bernie Sanders rallied thousands of voters in two New England states, seeking momentum even as he offered mixed signals on how hard he would push his differences with front-runner Hillary Clinton.
The Vermont senator largely steered clear of Clinton at a Rhode Island park, but hours later ramped up his critique before more than 14,000 supporters in New Haven, Connecticut. Sanders reiterated his call for Clinton to release transcripts of lucrative Wall Street speeches she delivered after leaving the State Department in early 2013.
"This campaign, unlike Secretary Clinton's, has not raised $15 million from Wall Street and millions more from other special interests," he said as the crowd booed at the mention of Clinton's name. "This candidate has not given speeches behind closed doors on Wall Street for $225,000 a speech."
Democrats downplaying tensions
Clinton eyed victories in four or five of Tuesday's contests, which would all but cripple Sanders' White House bid.
The former secretary of state went to two Philadelphia church services attended largely by African-Americans ahead of the primary in Pennsylvania, Tuesday's top delegate prize. She declined to attack her Democratic rival by name in the morning appearance and a subsequent stop in Bridgeport, Connecticut, focusing on the GOP candidates.
Democratic National Committee Chair Debbie Wasserman Schultz downplayed tensions between Sanders and Clinton, whose rivalry has become increasingly nasty in recent weeks.
"Regardless of the intensity of what's played out here ... we are going to be unified," she declared.
Peoples reported from Washington. Associated Press writers Kathleen Ronayne in Manchester, New Hampshire; Catherine Lucey in Philadelphia; Laurie Kellman in Washington; Jill Colvin in Hagerstown, Maryland; and Brian Slodysko in Terre Haute, Indiana; contributed to this report.