Having already dangled the possibility of delaying the recess as a motivational threat, Senator Chuck Schumer, Democrat of New York and the majority leader, warned colleagues about the prospect of working through the weekend. He has said he intends to hold votes before the August break on both the nearly $600 billion infrastructure deal and a $3.5 trillion budget blueprint set to carry much of the rest of Mr. Biden’s economic agenda.

The mood on Capitol Hill was grim, as private policy disagreements turned into public finger-pointing between the two parties. And a group that had been held up just days ago as the best chance for bipartisan success in a divided Congress was itself veering into dysfunction, with many senators tired of negotiating.

Perhaps it was an indication that the talks were just about to yield fruit, wallowing in the darkest moments of disagreement before a dawn when negotiators would work it all out. But it seemed just as likely they were headed toward collapse, confirming the expectations of legions of skeptics.