The distinguished gentlemen from the deep-red congressional districts swamped the aisle first — claiming their seats some five hours early with paper scraps, jackets and small electronics — earning televised cameos as President Trump arrived for the handshakes and great-to-see-ya’s.

A cleaning crew worked every corner of the grand chamber, running a vacuum over the royal blue carpet, kneading the underside of a railing with a rag. A man, wearing what appeared to be baseball batting gloves, adjusted a temporary light fixture beneath a less temporary chandelier in Statuary Hall. There, lawmakers spent their Tuesday afternoon staring into cameras and holding forth on what the president might say, should say, couldn’t say — and why it all mattered very, very much.

“It is what our country does,” Representative Steny H. Hoyer of Maryland, the Democratic whip, said of the exercise, strolling the Capitol as the finishing touches were applied. “And to that extent, it is reassuring.”