The logs were stacked high and flames filled the Oval Office fireplace as President Joe Biden sat next to President-elect Donald Trump on Wednesday. Biden smiled and extended his hand in welcome. It was a meeting Biden hoped could bring down the temperature in American politics but the halting introductions betrayed the awkwardness of the moment.

The letter expressed the Biden team’s readiness to assist with the transition, according to a pool report. During the Oval Office meeting, Trump lamented the brutality of today’s political climate. “Politics is tough, and in many cases, it’s not a ...