“That’s the path,” Speaker Nancy Pelosi declared, as she zipped between her office and the House chamber, surrounded by her security detail and a gaggle of reporters. “That’s the one we’re on. And it’s still on.”

Ms. Pelosi may be on a path, but with President Biden’s infrastructure bill still in limbo on Thursday evening, nobody in the Capitol seemed to know quite what that path was.

Ms. Pelosi had promised the House would vote Thursday on the bill. Instead, rank-and-file Democrats and members of the Democratic leadership team trooped in and out of the speaker’s suite on the second floor of the Capitol for much of the day, as Ms. Pelosi tried to round up the necessary votes to pass the measure.

Liberals were balking, insisting they would vote no unless the measure was paired with an expansive social policy bill. Moderates were frustrated; they need to show their constituents that they are doing something — anything — and are eager for the vote. The question of the day was: Would the bill come to the floor, as Ms. Pelosi had promised? Nobody seemed prepared to offer an unqualified “yes.”

“I don’t know,” Representative Jim Clyburn of South Carolina, the No. 3 House Democrat, told reporters who asked if the vote would come Thursday night. Mr. Clyburn is the Democratic whip — the leader responsible for counting (or in congressional parlance, “whipping”) votes. But for this bill, at least, it appears the one cracking the whip is Ms. Pelosi.

The No. 2 Democrat, Representative Steny D. Hoyer of Maryland, did not have much to add. Are you confident, he was asked, that if the bill came to the floor it would pass? “I’m confident that a majority of members are for it,” he said, leaving open the possibility that being for it and voting for it are not the same thing.

As afternoon headed toward evening, reporters were taking bets. Would the vote come at midnight? 1 a.m.? Later? Was there an ample supply of caffeine in the press gallery? Some in the Democratic rank and file were growing frustrated.

“We’ve been told over and over that we’re voting on this today,” said Representative Elissa Slotkin, a centrist Democrat from Michigan. “All the caucuses that I’m part of have been telling me that we’re voting on this today. We’re just waiting, for standby, on when.”

At 5:45 p.m., she got her answer — sort of. The House went into recess, with no votes scheduled until at least 9 p.m.