A defiant Bernie Sanders stood in front of a packed crowd in California Tuesday night and promised to continue his fight for the Democratic presidential nomination despite almost overwhelming odds.
"If this campaign has proven anything, it has proven that millions of Americans who love this country are prepared to stand up and fight to make this country a much better place," he said at the rally in Santa Monica. "Thank you all. The struggle continues."
Sanders spoke hours after Hillary Clinton claimed an historic victory, the first woman to be named the presumptive nominee of a major political party. The Associated Press made the declaration before California, New Jersey and four other states voted Tuesday.
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Sanders said he would compete in next week’s Democratic primary in Washington, D.C., the final contest, and pledged to bring his message of economic, racial and environmental justice to July's nominating convention. He said he wanted to use the momentum of the campaign to affect political change in America.
Still, he is coming under increasing pressure to withdraw so that Democrats can focus on Republican Donald Trump. Clinton was projected the winner of the biggest prizes of the night, California and New Jersey, as well as New Mexico and South Dakota, and had the majority of pledged delegates, according to NBC News. Sanders took North Dakota and Montana.
House Minority Leader Nancy Pelosi of California endorsed Clinton Tuesday morning, and The Associated Press reported that President Barack Obama was readying his formal support too.
He is in New York on Wednesday to address a Democratic National Committee fundraiser and to tape an appearance on "The Tonight Show Starring Jimmy Fallon" to air Thursday night, the AP noted.
The White House announced that Obama would meet with Sanders on Thursday at the senator's request.
"The President looks forward to continuing the conversation with Senator Sanders about how to build on the extraordinary work he has done to engage millions of Democratic voters, and to build on that enthusiasm in the weeks and months ahead," the statement said.
But Sanders has not backed away from trying to persuade superdelegates who have committed to Clinton to switch their support to him.
"Our goal is to get as many delegates as we possibly can and to make the case to superdelegates that I believe the evidence is fairly strong that I am the strongest candidate," Sanders said to reporters in California on Monday.
Lee Miringoff, director of the Marist Institute of Public Opinion, said that there was no indication Sanders would be able to convince superdelegates to switch allegiances.
"So there's not really a pathway for him at this point, a realistic one I should say," he said.
Clinton crossed the 2,383-delegate threshold needed to clinch the Democratic nomination Monday, and she frequently notes that she has accrued three million more votes in primaries and caucuses than Sanders.
Sanders told NBC News that he was upset about the timing of The AP's announcement and concerned about how it surveyed superdelegates about their commitments.
"They got on the phone as I understand it, and started hounding superdelegates to tell them in an anonymous way who they were voting for. The night before the largest primary, biggest primary in the whole process, they make this announcement," he said. "So I was really disappointed in what The AP did."
David Brady, a professor of political science at the Stanford University Graduate School of Business and a senior fellow at the Hoover Institution, said that both Hillary Clinton and former President Bill Clinton had long campaigned for Democrats and raised money for them. Sanders is an independent.
"He's never done anything for the Democratic party," he said. "This is his moment in the sun."
And his backers would be unlikely to vote for Trump, Brady said.
In a speech in New York Tuesday night, Trump appealed directly to those voting for Sanders.
"To all of those Bernie Sanders supporters who have been left out in the cold by a rigged system of superdelegates, we welcome you with open arms," he said.
He also went after Clinton, accusing her and her husband of selling access, favors and government contracts for hundreds of millions of dollars, attacking the former secretary of state's foreign policy record and appealing directly to Sanders' supporters.
Clinton made her first speech as presumptive nominee at the Brooklyn Navy Yard, introduced by a video focusing on barriers broken, from the suffragettes who gathered for a women's rights convention in Seneca Falls, New York, in 1848 to her candidacy.
"Thanks to you, we've reached a milestone -- the first time in our nation's history that a woman will be a major party's nominee," she said. "Tonight's victory is not about one person. It belongs to generations of women and men who struggled and sacrificed and made this moment possible."
She took the fight to Trump, saying he was temperamentally unfit to be president, a man who would take the United States backwards.
"When Donald Trump says a distinguished jurist born in Indiana can't do his job because of his Mexican heritage or he mocks a reporter with disabilities or calls women pigs, it goes against everything we stand for," she said. "Because we want an America where everyone is treated with respect."
She congratulated Sanders on an extraordinary campaign that had been good for the Democratic party and the United States and urged her audience to remember what united them as they looked to the battle ahead.
In his speech Tuesday, Sanders congratulated Clinton as well.
David McCuan, a professor of politics at Sonoma State University, called California the Disneyland of politics, more sizzle than steak, as Clinton sewed up the nomination.
But Sanders' goal is broader than the presidential race: He wants to remake the Democratic party and move it to the left, McCuan said. And he is preparing for future elections in 2018 and beyond, when both parties will be facing rapid demographic shifts, McCuan said.
"Part of the reason he's been here is about building a farm team up and down the ballot,” McCuan said.
Sanders hinted at that Tuesday. One of the lines that received the loudest, longest cheers was almost a statement of intent in which Sanders looked beyond the 2016 election: "We understand that our mission is more than just defeating Trump, it is transforming our country."
NBC's Asher Klein contributed to this report.