WASHINGTON — Choosing a single day that epitomizes Donald J. Trump’s presidency — amid the endless tangle of jaw-dropping, reality-bending, norm-shattering days — is a fool’s errand. But for a White House correspondent departing the beat after eight years, Thursday came awfully close.

From Mr. Trump’s morning Twitter rant (asking how anyone could vote for a Democrat over “what you have now, so great looking and smart, a true Stable Genius!”) to his social media summit (in which he praised a room of right-wing agitators for “the crap you think of”), to a news conference that ended with his merry band of provocateurs almost coming to blows with reporters, the White House finally surrendered itself to being a stage set for Mr. Trump’s greatest reality show.

It is not that real business wasn’t transacted there on Thursday. Mr. Trump went to the Rose Garden to announce his retreat, in the face of a Supreme Court ruling, from asking a question about citizenship on the 2020 census. But he upstaged his own effort to spin the defeat — by promoting actions that were underway already — with a theatrical outburst.

“Are you a citizen of the United States of America?” Mr. Trump said to reporters, sarcastically mimicking a data collector for the Census Bureau. “Oh, gee, I’m sorry, I just can’t answer that question.”