President Trump on home turf, the South Lawn of the White House, on Saturday. (Ron Sachs/Cnp)
Angus Johnston is a historian of American student activism. He teaches history at the City University of New York.

In an extraordinary exchange of letters Wednesday, President Trump and House Speaker Nancy Pelosi delivered mutually exclusive ultimatums, leaving next week’s planned State of the Union address in limbo. In the first letter, Trump declared flatly that despite Pelosi’s Jan. 16 postponement, he would be delivering his speech as originally scheduled: “I will be honoring your invitation, and fulfilling my Constitutional duty,” he wrote. “I look forward to seeing you on the evening on January 29th in the Chamber of the House of Representatives.” Hours later, though, Pelosi was just as emphatic: “the House of Representatives will not consider a concurrent resolution authorizing the President’s State of the Union address in the House Chamber until government has opened.”

No deal, no speech. Period.

Faced with this irresistible-force-meets-immovable-object spectacle, D.C. observers for much of Wednesday immersed themselves in the minutiae of government protocol (Trump can go to the House chamber whenever he wants! But he can’t turn on the lights without permission! And Pelosi controls the C-SPAN cameras!), with several suggesting that Trump might simply call Pelosi’s bluff and show up on Tuesday night, figuring that she’d either give in and let him speak or lose the optics battle by refusing.

But let’s be real — that was never going to happen. That kind of showdown isn’t in Trump’s nature.

Heck, even traveling the two miles from the White House to the Capitol without a written invitation would be practically unprecedented. Trump hates leaving his home turf. Hates it. He only emerges from his cocoon when he’s promised he’ll be coddled and catered to, and frequently bails even then. He vacations almost exclusively at properties he owns. On the campaign trail he does rallies, not meet-and-greets. On his last trip to Europe he played hooky at an Armistice Day commemoration. It took him nearly two years to visit the troops in Iraq, and he still hasn’t been to Afghanistan.

And for all his bluster, Trump is almost comically conflict averse. He delivers insults via tweet or television camera, not face-to-face. He habitually ducks firing Cabinet members and senior staff, forcing underlings to lower the boom for him. Unscripted confrontation — a real fight, for real stakes — just isn’t in him.

So why has the myth of Trump as an eager street fighter persisted for so long? It’s largely an artifact of his popularity with Republican Party voters. With the GOP holding the reins of power throughout the federal government in the first half of his term, and staying in his good graces essential to other Republicans’ hopes of winning their home-state primaries, Trump has been free to provoke confrontations whenever and wherever he wanted without fear. He might be outplayed in these fights, and he might be manipulated, but he could not be humiliated, and he would not lose face.

But that changed with the coming of the Democratic majority in the House of Representatives this month. Now, for the first time in his presidency, Trump has adversaries in Congress who will pay no price at the polls for crossing him, opponents he can’t count on to take a dive before the final bell.

Which brings us to Wednesday. At 12:21 p.m., White House press secretary Sarah Sanders tweeted the text of his letter to Nancy Pelosi in which he announced that he would be giving the State of the Union in the House chamber. At 3:17 p.m., Pelosi tweeted her response, saying that he would not be. And how did Trump respond? He caved immediately, announcing on camera less than an hour later that “the State of the Union has been canceled by Nancy Pelosi.” Late last night he went further, conceding that it was Pelosi’s “prerogative” to cancel the address, and announcing that he would work with her to reschedule it after the government shutdown ends.

Trump, it turns out, is only good at throwing his weight around when nobody calls his bluff. His reputation for interpersonal aggressiveness is a mirage, an artifact of reality television and the internal dynamics of the Republican electorate. (There was that incident in Brussels when he shoved the prime minister of Montenegro out of his way, but even then he couldn’t bring himself to make eye contact, and there was basically no chance he would be shoved back.)

He still has plenty of power, of course, and he is likely to gain more political victories before leaving office — he’s the president of the United States, after all. But confronted with an actually immovable object, the supposedly irresistible force revealed itself as downright . . . resistible.