A Coming Collision

The postelection fraud claims quickly exposed a rift within the Trump family. On the same day Mr. Kushner woke up to declare it was time to move to Miami, his brother-in-law Donald Trump Jr. was already pushing the president’s team to fight to stay in power. He sent a text to Mark Meadows, the White House chief of staff, outlining a plan to override the verdict of the voters by having Republican legislatures in states won by Mr. Biden invalidate the results and send Electoral College votes for Mr. Trump when Congress counted them on Jan. 6.

How much Mr. Kushner knew about that at the time remains unclear, but he did not express serious concern about how far the effort to hang on to power would go. He sent word to Senator Mitch McConnell of Kentucky, the Republican majority leader, that Mr. Trump would eventually accept the reality that he lost.

“We’ll get through it, bear with us,” Mr. Kushner told Josh Holmes, a former chief of staff and campaign manager for Mr. McConnell who would pass along the message. “We’ve got a couple of challenges that have some merit, we’ll see how they go, but there’s a pretty good chance we come up short.” And once the Electoral College voted on Dec. 14, he suggested, that would be the end of it. Mr. Trump just needed time to come to terms with his defeat.

While Mr. Kushner was often called the president’s shadow chief of staff, the man who held the actual title, Mr. Meadows, was actively encouraging the conspiracy theorists seeking to overturn the election, acting less as a gatekeeper than a door opener, letting practically anybody who wanted to come into the Oval Office.

Among them were lawyers and others arguing that Vice President Mike Pence could unilaterally stop Mr. Biden from being formally recognized as the winner in his role overseeing the counting of the Electoral College votes in Congress. Mr. Pence concluded he had no such power and it would be unconstitutional for him to do so, but that did not stop Mr. Trump from keeping up the pressure.

Finally, seeing the collision that was coming, Marc Short, the vice president’s chief of staff, tried to enlist help from Mr. Kushner, calling him over the holidays to ask him to get his father-in-law to stand down. “Look, can you help us with this?” Mr. Short asked.