Pence has reached his limit with Trump. It was not pretty.

In the Oval Office last week, the day before the vote, Mr. Trump pushed Mr. Pence into a series of meetings, including one that lasted at least an hour. John Eastman, a conservative constitutional scholar at Chapman University, was in the office and argued to Mr Pence that he had the power to act.

The next morning, hours before the vote, Richard Cullen, Mr Pence’s personal lawyer, called J. Michael Luttig, a former appeals court judge revered by the Tories – and for whom Mr Eastman had already been a clerk. Mr Luttig agreed to quickly write his opinion that the vice president did not have the power to change the outcome, and then posted it on Twitter.

Within minutes, Mr Pence’s staff incorporated Mr Luttig’s reasoning, citing him by name, into a letter announcing the Vice President’s decision not to try to block voters. Arriving on Tuesday, Mr Luttig said it was “the greatest honor of my life” to play a role in preserving the Constitution.

After the angry call insulting Mr. Pence, Mr. Trump angered supporters of the rally against his own vice president, saying, “I hope he doesn’t listen to the RINOs and the stupid people that ‘He listens.

“He prepared Mike Pence that day by putting him on his shoulders,” said Ryan Streeter, Mr. Pence’s adviser when he was governor of Indiana. “It’s a pretty unprecedented thing in American politics. For a president to throw his own vice president under the bus like that and encourage his supporters to take him is something just plain wrong in my mind.

Mr. Pence was already in his procession at the Capitol by this time. When the crowd broke into the building, Secret Service agents evacuated him and his wife and children, first to his office on the floor, then to the basement. His agents urged him to leave the building, but he refused to abandon the Capitol. From there, he spoke to leaders of Congress, the Secretary of Defense and the Chairman of the Joint Chiefs of Staff – but not the president.

A Republican senator later said he had never seen Mr Pence so angry, feeling betrayed by a president he had done so much for. To Mr. Trump, an adviser said, the vice president had entered “session territory,” referring to Jeff Sessions, the attorney general who was tortured by the president before being fired. (A vice-president cannot be removed by a president.)