Infrastructure remains stuck near the rear of the legislative line, according to two dozen administration officials, legislators and labor leaders involved in coming up with a concrete proposal. It awaits the resolution of tough negotiations over the budget, the debt ceiling, a tax overhaul, a new push to toughen immigration laws — and the enervating slog to enact a replacement for the Affordable Care Act.

Mr. Trump’s team has yet to produce the detailed plan he has promised to deliver “very soon,” and the president has yet to even name any members to a new board he claimed would green-light big projects.

The collapse of his health care overhaul effort seemed to clear one item out of the way. But it also raised serious doubts about the ability of Republicans to pass anything other than regulatory rollbacks or routine spending bills.