Indianapolis: Republican Donald Trump and Democrat Hillary Clinton rapidly turned their fire on each other with an eye toward November's presidential election after rolling up strong wins in Northeastern states.
The New York billionaire easily defeated rivals John Kasich and Ted Cruz in all five states that held party nominating contests on Tuesday - Pennsylvania, Maryland, Connecticut, Rhode Island and Delaware. He had a margin of victory rivaling that of New York state a week ago and was on course to win the vote in every county in each state.
Clinton, already in control of the Democratic race, defeated challenger Bernie Sanders in Maryland, Delaware, Pennsylvania and Connecticut. Her only loss of the night was in Rhode Island.
The race now pivots immediately to Indiana, which is shaping up to be Cruz's best, and perhaps last, chance to slow Trump's momentum toward capturing the Republican presidential nomination for the November 8 general election.
If Cruz, a US senator from Texas, can win a large share of the state's 57 delegates on May 3, it will boost the chances that Trump will not be able to amass the 1,237 delegates he needs to clinch the nomination before the party's convention in July. That could give Cruz a shot at convincing delegates to back him for president instead.
Cruz's campaign has begun hinting that he could name a vice presidential running mate as soon as this week, a move that would seek to consolidate more Republican support and create an image that he will be the nominee. Former Hewlett Packard CEO Carly Fiorina, who made a failed presidential bid, is among the potential picks being vetted.
Trump, pressing his point that he views the nominating race as essentially finished, criticized that as a potential Cruz pick. "I think it would be a bad choice, not because she's a woman but because she did not resonate at all with people."
"It's too early to do it. And frankly, he's wasting his time because he's not going to be the nominee," Trump said.
A loss to Trump in Indiana would effectively cripple Cruz's already faltering bid, and increase pressure on the party to rally around Trump as the prospective nominee.
As Trump has moved from longshot candidate in a crowded field last year to clear front-runner, he has sparked despair among many in the Republican establishment both for his aggressive and sometimes insulting style and for campaign pledges such as slapping a temporary ban on Muslims entering the country, and building a wall along the border with Mexico.
Katie Packer, head of the anti-Trump political-action committee Our Principles, said her organization would be active in Indiana with "TV, mail, phones, digital, all of it".
"We're going to be playing in a lot of different congressional districts," Packer said.
The Club for Growth, a conservative pro-business group, has bought $1.5 million worth of anti-Trump TV ads in the state.
Both groups worked to hand Trump a defeat at the hands of Cruz earlier this month in Wisconsin.
"Tonight, this campaign moves back to more favorable terrain," Cruz said in Knightstown, Indiana on Tuesday.
Back on the East Coast, Trump and Clinton used victory rallies to snipe at each other, a taste of the kind of back and forth that will take place should they win their party's nominations and face off in the general election campaign.
"I think she's a flawed candidate and she's going to be easy to beat," Trump told a news conference at New York's Trump Tower.
In an interview on Wednesday morning with ABC's "Good Morning America," he said he was not concerned that supporters of his Republican rivals would not back him against Clinton.
"They're going to come over," said Trump, a real estate magnate and former reality TV star. "I've watched it all my life. They are angry, they're confused, and they don't know how all of this has happened, then all of a sudden it turns into love. Anger turns into love."
Trump was due to give a big foreign policy speech in Washington on Wednesday. He criticised Clinton's record as secretary of state and her vote as a US senator from New York in support of the Iraq war. He said her only advantage was her bid to be the first woman US president.
"Frankly if Hillary Clinton were a man, I don't think she'd get 5 per cent of the vote," he said.
Clinton, in a victory speech in Philadelphia, took aim at Trump for accusing her of trying to "play the woman card."
"Well if fighting for women's healthcare and paid family leave and equal pay is playing the woman card, then deal me in," she said to cheers.
Of 118 committed delegates available on Tuesday, Trump took 105, raising his total delegates to 950. Kasich, the Ohio governor, won five, all from Rhode Island, and Cruz one, with seven delegates still to be assigned, according to the Associated Press. Pennsylvania's 54 unbound delegates will become clearer later.
Clinton's strong showing in the Democratic race added to the pressure on Sanders to get out of the race or ease his criticism of her.
In her speech Clinton was careful, however, to avoid criticizing Sanders, a US senator from Vermont, as she spoke of the need for party unity.
"Whether you support Senator Sanders or you support me, there is much more that unites us than divides us," she said.
Clinton's victories on Tuesday brought her total count to 2,141 delegates, according to the AP, pushing her closer to the 2,383 needed for the nomination.
Sanders, who has accused Clinton of being in the pocket of Wall Street and pledged to do more than she would to address social inequality, showed no signs of getting out of the race. He is expected to campaign in Indiana.
"The people in every state in this country should have the right to determine who they want as president and what the agenda of the Democratic Party should be. That's why we are in this race until the last vote is cast," he said in a statement on Tuesday night.