The crowd cheered and the music blared.

On Monday night outside the D.C. jail, some of the family members, fervent supporters and former detainees gathered there swiveled their hips and pumped their fists to a remix of “Y.M.C.A.,” in a scene reminiscent of a Trump rally.

They were there to celebrate President Trump’s broad grant of clemency to nearly all 1,600 Jan. 6 defendants, though only a dozen of those pardoned remained in this particular jail on the morning of his inauguration. The nightly vigil, which has lasted for close to two and a half years, has served as the emotional epicenter of support for those who have been prosecuted in connection with the violent attack on the Capitol four years ago.

Micki Witthoeft, the mother of Ashli Babbitt, an Air Force veteran who was fatally shot by the police as rioters tried to storm the building on Jan. 6, 2021, typically kicked off the gathering with a roll call of all the detainees across the country. But not on Monday.

“We’re going to skip that tonight because it’s just a variable,” Ms. Witthoeft said. “Everybody’s getting out.”

Only two men, Andrew and Matthew Valentin, brothers who were sentenced just days ago, walked free on Monday, according to Paul Ingrassia, the newly appointed White House liaison to the Justice Department.