A confident Donald Trump told supporters on Saturday that he's not changing his pitch to voters, a day after his chief adviser assured Republican officials their party's front-runner would show more restraint while campaigning.

Trump revived his birther criticism of rival Cruz, which he has previously used to suggest the Texas senator is ineligible to run for president.

"Rafael! Straight out of the hills of Canada!" he declared, referring to Cruz by his given name. Most experts say that Cruz is eligible to serve in the White House even though he was born to an American mother on Canadian soil, but Trump has worked to sow doubts.

"You know, being presidential's easy — much easier than what I have to do," he told thousands at a rally in Bridgeport, Connecticut. "Here, I have to rant and rave. I have to keep you people going. Otherwise you're going to fall asleep on me, right?"

Trump declared to the crowd that he has no intention of reversing any of his controversial policy plans, including building a wall along the length of the Southern border.

"Everything I say I'm going to do, folks, I'll do," he said.

Trump's new chief adviser, Paul Manafort, met Thursday with top Republican officials and told them his candidate, known for his over-the-top persona and brashness, has been "projecting an image."

"The part that he's been playing is now evolving," Manafort said.

At a rally in Waterbury, Connecticut, earlier Saturday, Trump joked about how it's easy to be presidential, making a series of faux sombre faces. But he told the crowd he can be serious and policy-minded when he has to be.

Manafort "said, `you know, Donald can be different when he's in a room.' Who isn't," asked Trump. "When I'm out here talking to you people, I've got to be different."

5 states hold primaries on Tuesday

The Republican front-runner and most of his rivals in both parties were out campaigning Saturday across the quintet of Northeastern states holding primaries on Tuesday, including Pennsylvania, Delaware, Maryland, Rhode Island and Connecticut. For the Republicans, in particular, the stakes are high as Trump looks to sweep the remaining contests and reach the required 1,237 delegates needed to clinch the nomination, while his rivals Ted Cruz and John Kasich look to thwart his efforts and force the race into a contested convention.

Trump greets supporter Evabeth Kloc, right, after speaking during a campaign rally at Crosby High School, in Waterbury, Connecticut on Saturday. (Eduardo Munoz/Reuters)

Cruz, in Pennsylvania on Saturday, addressed around 1,000 supporters in a high school outside Pittsburgh, and though the reception was raucous, the crowd didn't know how to react to the Texas senator's opening by saying, "Let me say something that is profoundly painful for someone who grew up as a fan of the Houston Oilers, God bless the Pittsburgh Steelers."

Cruz said Tuesday "is going to be a pivotal day," but he also travelled on Saturday to Indiana, which doesn't vote until next month. Trump is thought to be favoured in Pennsylvania, while Cruz's deep evangelical roots could give him a boost in Indiana.

Cruz also rebuked Trump's recent suggestions that building separate transgender bathrooms is "discriminatory" and costly, saying Saturday that it should be "the choice of the given location, of the given local government to allow that, to provide for that."

Dems duke it out

Democratic front-runner Hillary Clinton also campaigned in Connecticut on Saturday, where she held a round-table event in New Haven with working families to discuss the need to raise the federal minimum wage from $7.25 an hour. Clinton also discussed her policy proposals to provide equal pay for women.

Clinton's rival, Bernie Sanders, meanwhile, spoke to a boisterous crowd of mostly young people in Baltimore where he railed against big banks and highlighted his differences with Clinton on everything from the minimum wage to free trade agreements.

He hammered at "disastrous trade policies," describing them as not a sexy issue but an important issue, saying that "we are seeing corporation after corporation shut down in the United States throw millions of workers out in the street, people who are earning a living wage."

"I oppose every one of these disastrous trade agreements. She supported almost every one of them," he said, referring to Clinton, to a chorus of cheers.

A day earlier, Sanders responded to questions by MSNBC over whether he would campaign for Clinton if she wins the nomination and rally his young supporters behind her.

"I've got to find out what her platform is, what the views are that she is going to be bringing forth, to what degree she will adopt many of the ideas that I think are extremely popular and I think very sensible," Sanders said.