“You think you’ve got gridlock now?” said Senator Carl Levin, Democrat of Michigan. “You think you’ve got problems now? You will have a huge, huge outpouring of real anger.”

“That means the next Senate,” he added, “if the Republicans control it, you can expect them by majority vote to put through any rules change they want.”

But the level of frustration among Democrats now has pushed many of them, including Mr. Reid, to believe that the situation has deteriorated so badly that it can be fixed only by doing something they once would have never considered.

The level to which the squabbling over nominees has sunk was vividly evident on Thursday as the Environment and Public Works Committee voted to send Ms. McCarthy’s nomination to the full Senate. Republicans on the committee boycotted a vote scheduled for last week, leaving Democrats without a quorum.

That left Senator Barbara Boxer, Democrat of California and the committee chairwoman, with no other way to obtain a quorum but to round up Senator Frank R. Lautenberg, the ailing New Jersey Democrat who has been largely absent from the Senate in recent weeks. Mr. Lautenberg appeared on Thursday to cast his vote, as did Republicans. All eight of them voted no, and Ms. McCarthy’s nomination was reported out of committee by a 10-to-8 party-line vote.

Republicans said they could not vote yes because they believe that Ms. McCarthy and the E.P.A. have not been sufficiently transparent, including what they said was a failure to adequately answer almost 1,100 questions that they submitted. “We’re asking for openness and transparency as required by law,” said Senator David Vitter of Louisiana, the committee’s ranking Republican.

During the vote for Mr. Perez, who was reported out of the Committee on Health, Education, Labor and Pensions with a 12-to-10 vote, Senator Tom Harkin, the chairman, said that Republican efforts to block the nomination were not based on any legitimate concerns. “That was just delay for delay’s sake,” he said.