President Biden will depart Washington today for a two-day trip to New York, turning his attention away from swing states to campaign and raise funds in a liberal stronghold.

Mr. Biden, 81, will be joined tonight at a campaign fund-raiser in Manhattan by his two most recent Democratic predecessors: Barack Obama and Bill Clinton.

The star-studded event, at Radio City Music Hall, is aimed at building on the already significant financial advantage Mr. Biden has over his opponent, former President Donald J. Trump. Campaign finance records released last week showed that Mr. Biden’s campaign had more than twice as much cash on hand as Mr. Trump’s campaign — a gap of nearly $40 million.

And it is likely to be just the beginning of the effort by Mr. Obama, 62, who left office seven years ago, and Mr. Clinton, 77, who left office over 23 years ago, to lift the president’s re-election campaign ahead of his rematch against Mr. Trump in the fall.

Mr. Obama in particular has expressed grave concerns that Mr. Biden could lose to Mr. Trump and is making regular calls to top aides at the White House to strategize and offer advice. He had previously played a crucial role in wrapping up the 2020 primaries after it became nearly certain that Mr. Biden would be the nominee.

Mr. Obama and Mr. Clinton both campaigned on Mr. Biden’s behalf in the 2020 race and made main-stage speeches at that year’s Democratic National Convention. The two have since offered the president their counsel during his term and have visited the White House and promoted their policy achievements alongside Mr. Biden.

Hillary Clinton, the Democratic presidential candidate in 2016, had meanwhile made some effort to eschew campaign politics during her own appearance at the New York Public Library on Wednesday evening. But Mrs. Clinton could not entirely avoid questions about Mr. Trump and the coming election. She said that Americans should ensure that Mr. Trump “is never president ever again.” She was also asked whether she found Mr. Trump’s felony indictments “gratifying.”

“I am not answering that question,” she said with a smile and a vigorous shake of her head.