At the White House, Mr. Trump has been toggling between appearing to recognize his loss and expressing bitterness and disbelief that what he believed was a victory was being taken from him, aides said. Bolstered by some core supporters, he has hardened in his belief that state legislatures could hold the keys to his political salvation.

The few people who have tried to intervene and tell him that it is time to let Mr. Biden begin a transition have been shut down by Mr. Trump.

The president has been goaded along in particular by his personal lawyer Rudolph W. Giuliani, who has further stoked Mr. Trump’s fury, along with his hope of overcoming the reality of Mr. Biden’s victory, a half-dozen White House and campaign advisers said.