Democrats were on the other side, coaxing him to put off the vote. Senator Chris Coons, Democrat of Delaware, a longtime friend, broke in: This is a mess, he said, and to lift the cloud over Judge Kavanaugh, an investigation was necessary.

But what could really be done in a week? There was a scramble to call Christopher Wray, the F.B.I. director, who could not be reached. The second choice was Rod J. Rosenstein, the deputy attorney general.

Mr. Coons and Mr. Flake squeezed into an oversize phone booth — a few still exist on Capitol Hill — to make the call. They needed privacy rather than a landline, so held a cellphone on speaker between them. Mr. Rosenstein told them the F.B.I. could complete a background check in a week, although it was unlikely to unearth much more than was already known.

Minutes later, Mr. Flake, a pained expression on his face, returned to the committee room and made the announcement ensuring that the F.B.I. investigation would go forward — and once again upending Washington.