Thursday the 12th was the day Mr. Trump’s flimsy, long-shot legal effort to reverse his loss turned into something else entirely — an extralegal campaign to subvert the election, rooted in a lie so convincing to some of his most devoted followers that it made the deadly Jan. 6 assault on the Capitol almost inevitable…

In the Senate, he got early room to maneuver from the majority leader, Mitch McConnell. As he sought the president’s help in Georgia runoffs that could cost him his own grip on power, Mr. McConnell heeded misplaced assurances from White House aides like Jared Kushner that Mr. Trump would eventually accede to reality, people close to the senator told The Times. Mr. McConnell’s later recognition of Mr. Biden’s victory would not be enough to dissuade 14 Republican senators from joining the president’s last-ditch bid to nullify millions of Americans’ votes.

Likewise, during the campaign, Attorney General William P. Barr had echoed some of Mr. Trump’s complaints of voter fraud. But privately the president was chafing at Mr. Barr’s resistance to his more authoritarian impulses — including his idea to end birthright citizenship in a legally dubious pre-election executive order. And when Mr. Barr informed Mr. Trump in a tense Oval Office session that the Justice Department’s fraud investigations had run dry, the president dismissed the department as derelict before finding other officials there who would view things his way.