Surrounded by a handful of trusted advisers and First Lady Jill Biden at his vacation home on the Delaware coast Saturday evening, President Joe Biden reflected on a political career that spanned back more than half a century and began to conclude that it would reach its end earlier than planned, according to people familiar with his decision.

Isolated, frustrated and angry, he felt betrayed by allies who turned on him in his hour of need. 

“He’s really pissed off,” said one person in…