Hillary Clinton and Donald Trump were a giant step closer to their parties' presidential nominations Wednesday after crushing their respective Democratic and Republican rivals in a string of presidential primaries.
Clinton has now virtually cleared the way to become the Democratic nominee in the November presidential election, the first woman in US history to reach that milestone.
The former secretary of state won four out of five primaries Tuesday in Connecticut, Delaware, Maryland and the night's big prize, the battleground state of Pennsylvania.
She conceded only the small state of Rhode Island to rival Bernie Sanders in a near sweep that gives her an almost insurmountable delegate lead.
Clinton now has 2,168 delegates, including more than 500 "super-delegates," against Sanders's 1,401, with about 1,000 more to be distributed in the 14 remaining nominating races. She needs 2,383 delegates to win the nomination.
"What a great night," Clinton told a thrilled crowd of supporters in Philadelphia, Pennsylvania.
The 68-year-old former first lady telegraphed her eagerness to shift toward the general election and a showdown with Republicans.
"Let's go forward, let's win the nomination, and in July let's return as a unified party," she said.
Clinton's strong showing heaps pressure on the well-funded Sanders, a self-styled democratic socialist senator from Vermont who vowed to battle on until the California primary on June 7.
"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," Sanders said in a statement.
"That is why this campaign is going to the Democratic National Convention in Philadelphia with as many delegates as possible to fight for a progressive party platform."
Trump swept all five presidential races held Tuesday, strengthening his grip on the Republican race.
He demolished his rivals Ted Cruz and John Kasich in Connecticut, Delaware, Maryland, Pennsylvania and Rhode Island -- a stunning show of force by a candidate seen as a populist political savior by millions despite being loathed by the party establishment.
"I consider myself the presumptive nominee," the real estate mogul told a crowd at Trump Tower in New York, despite still being short of the 1,237 delegates required to win the nomination outright.
"As far as I'm concerned, it's over."
The 69-year-old billionaire extended his lead in the delegates who will officially choose the Republican nominee at the party's convention in July.
"For weeks, the stop Trump, dump Trump movement has tried to puncture" his rise, James Morone, a political science professor at Brown University, told AFP.
"Today's results overwhelmingly tell you it's not working."
Trump also offered a preview Wednesday of what a Trump-Clinton matchup would look like, repeating on CNN his assertion that Clinton is "playing the woman card left and right."
But at her victory party in Philadelphia, Clinton told supporters that "if fighting for women's health care and paid family leave and equal pay is playing the woman's card, then deal me in."
Trump's triumph comes after Cruz and Kasich teamed up to try and to block the Republican frontrunners path in several upcoming primaries.
Trump slammed the alliance as "pathetic" and ineffective.
"This joke of a deal is falling apart, not being honored and almost dead," Trump said on Twitter. "Very dumb!"
A key test will come in Indiana which votes May 3. Kasich has agreed not to campaign there, giving Cruz an opportunity to compete head to head with Trump for the state's 57 delegates.
Trump now stands at 988 delegates, according to CNN's running estimate. Cruz was a distant second with 568, while Kasich increased his numbers only slightly, to 152.
But the convoluted system of delegate allocation in some states means Trump is still a considerable way from reaching 1,237.
Out of Pennsylvania's 71 delegates, only 17 are pledged to the winner, Trump. The remaining 54 are essentially wildcards, heading unpledged to the convention where they are free to vote as they see fit.
If Trump falls short of outright victory, he runs the risk that his delegates, most of whom are bound to vote for him in only the first round, will desert him in subsequent rounds.
Cruz and Kasich have openly said they are counting on a contested convention, where they have a shot at wooing enough delegates to snatch the nomination.
Trump recently faced criticism when a top aide revealed the candidate was preparing to reshape his image, but Trump insisted Wednesday morning he was not undergoing a makeover.
"I'm not going to be changing. I'm presidential anyway," he told CNN.