David Jackson

USA TODAY

WEST CHESTER, Pa. — Donald Trump looks to sweep five northeastern states Tuesday while preparing for a revamped Republican race against an extraordinary alliance between rivals Ted Cruz and John Kasich designed to stop him at the July convention.

Denouncing plans by Cruz and Kasich to avoid each other in three upcoming states, Trump told supporters packed into an old gym at West Chester University in Pennsylvania that the deal amounts to "collusion" that illustrates what a "dirty business" politics is.

Echoing comments he made at an earlier rally in Warwick, R.I., Trump said the Cruz-Kasich alliance is "going to make them look weak and pathetic — which they are."

With Trump favored to win Tuesday in Pennsylvania, Connecticut, Maryland, Delaware and Rhode Island, Cruz and Kasich sought to reset the overall race with a unique deal.

The Cruz campaign will focus on the May 3 primary in Indiana without opposition from Kasich, while Kasich will take on Trump in future primaries in Oregon (May 17) and New Mexico (June 7), aides said -- though the candidates themselves offered somewhat different assessments of the impact of their agreement.

John Kasich, Ted Cruz team up against Donald Trump

Kasich, speaking with reporters in Pennsylvania, said "we haven't spent a lot of resources" in a lot of states anyway.

Asking "what's the big deal?" the Ohio governor added that his supporters in Indiana "ought to vote" for him if they want to — a position that Trump mocked on Twitter as evidence that Kasich is a "typical politician" who "can't make a deal work."

Cruz, campaigning in Indiana, told reporters that Trump would lead Republicans to a "landslide" loss in November, and said his agreement with Kasich makes the Hoosier State "a crossroads" in the election overall. "We're at a fundamental fork in the road," the Texas senator said.

The Cruz campaign also announced it has developed a short list of potential vice presidential nominees.

Reports: Ted Cruz vetting Carly Fiorina for VP

Trump currently leads the delegate race by nearly 300 votes. He has 845 delegates to Cruz's 559, according to the Associated Press, with Kasich back at 148.

Another 172 delegates are at stake in Tuesday's five primaries. One wrinkle is in Pennsylvania, where 54 of the 71 will be unbound regardless of the vote, and therefore subject to lobbying by all three candidates.

Republicans fight for Pennsylvania's free-agent delegates

Cruz and Kasich are underdogs Tuesday, in part because they appeared to be splitting anti-Trump votes in several states. Each candidate has accused the other of taking their votes, and argued that a vote for either is essentially a vote for the front-running Trump.

Cruz left Pennsylvania on Saturday and has been campaigning in Indiana in the days since. Kasich, who was born in Pennsylvania, campaigned there Monday, and canceled events he had planned for Indiana on Tuesday.

Trump, meanwhile, is predicting success in Indiana. His campaign announced a Wednesday evening rally in Indianapolis featuring former Indiana University basketball coach Bob Knight, an event that comes just hours after Trump delivers what aides call a major foreign policy address.

Game changer? Bobby Knight to campaign with Trump in Indiana

During his appearance in West Chester, Pa., Trump predicted that the new Cruz-Kasich agreement "is going to have a huge reverse effect."

The Cruz and Kasich campaigns also made clear they would compete against each other, and Trump, in other upcoming contests, including California, New Jersey, and Washington.

Both candidates are looking to prevent Trump from securing a majority of delegates — 1,237 — on the first ballot at the GOP convention that starts July 18 in Cleveland.

Delegates who are required to back certain candidates on the first ballot would be unbound on subsequent ballots, and Cruz and Kasich both believe that many who are now obligated to Trump will defect to them in an open convention.

Trump plans to woo potential delegates on his own by visiting state Republican conventions in California and Virginia at the end of the week. He told backers at his rallies on Monday that he will prevail on the first ballot at the convention.

G. Terry Madonna, a political scientist at Franklin & Marshall College in Lancaster, Pa., questioned whether the new Cruz-Kasich alliance would work, saying it "feeds the narrative that the establishment is intriguing to stop Trump. It plays right into his message."

Given Trump's likely wins on Tuesday, Madonna said, "it borders on a last-ditch tactic, and Trump will use it for all its worth."

Republican pollster Frank Luntz called it a "brilliant strategy," but with "disastrous execution" that allows Trump to cast the plan as rigged politics.

"The fact that they are talking about it completely undermines its otherwise effectiveness," Luntz said. He added: "It looks to outsiders like the insiders are trying to control the convention when it should be up to the people to decide."

In criticizing the deal, Trump said, "because of me, everyone now sees that the Republican primary system is totally rigged."

Members of the "Stop Trump" movement said they hope the Cruz-Kasich alliance will help, but no one can be sure because it is such a unique strategy.

“Whether you support Ted Cruz or John Kasich, a second ballot at the convention is imperative to stopping Donald Trump," said Rory Cooper, an adviser for the group #NeverTrump.

Liz Mair, a Republican consultant who founded the anti-Trump political committee action committee Make America Awesome, said the Cruz-Kasich alliance should help stop the New York businessman.

"I think there's a good chance," she said. "But that also means there's a chance it won't."