Sick with Covid and abandoned by allies, President Biden has been fuming at his Delaware beach house, increasingly resentful about what he sees as an orchestrated campaign to drive him out of the race and bitter toward some of those he once considered close, including his onetime running mate Barack Obama.

Mr. Biden has been around politics long enough to assume that the leaks appearing in the media in recent days are being coordinated to raise the pressure on him to step aside, according to people close to him. He considers Representative Nancy Pelosi, the former House speaker, the main instigator, but is irritated at Mr. Obama as well, seeing him as a puppet master behind the scenes.

The friction between the sitting president and leaders of his own party so close to an election is unlike anything seen in Washington in generations — especially because the Democrats now working to ease him out were some of the allies most critical to his success over the last dozen years. It was Mr. Obama who elevated Mr. Biden from a presidential also-ran to the vice presidency, setting him up to win the White House in 2020, and it was Ms. Pelosi and Senator Chuck Schumer, the Senate Democratic leader, who pushed through his landmark legislative achievements.

But several people close to Mr. Biden, who insisted on anonymity to discuss internal matters, described an under-the-weather president coughing and hacking more than a hundred miles from the corridors of power as his presidency meets its most perilous moment.

He has watched with rising exasperation as a succession of news stories appeared, one after the other, reporting that Mr. Schumer, Ms. Pelosi, Mr. Obama and Representative Hakeem Jeffries of New York, the House Democratic leader, all had warned of a devastating defeat for the party in November.

And he certainly noticed that Mr. Obama has not done anything to help him in recent days even as his own former aides publicly have led the way in calling on Mr. Biden to withdraw in what was interpreted, rightly or wrongly, as a message from the former president’s camp. The unseen but clearly felt presence of Mr. Obama in particular has brought a Shakespearean quality to the drama now playing out, given their eight-year partnership.