“If you believe in limited government, the filibuster has been your friend far more than your foe,” said Senator Jeff Flake, Republican of Arizona, who, like many other senators, was adamant that he would not support a weakening of the tactic.

Until Mr. Trump’s latest outburst, the fate of the legislative filibuster was far from assured.

Harry Reid, Democrat of Nevada and the former majority leader, predicted last year that Democrats would try to jettison the filibuster if Hillary Clinton won the presidency and Democrats won the Senate, only to see Republicans continue the stalling tactics they employed so successfully against President Barack Obama. And Democrats had already shown a willingness to make changes with their 2013 maneuver to eliminate the 60-vote threshold for most judicial and executive branch nominees.

Then Mr. Trump’s victory completely turned the tables, with the Republicans who now controlled Congress and the White House ruminating about gutting the filibuster if Democrats stood in the way of the Trump agenda. Republicans in the House and conservative groups cheered on the idea, saying it could finally break a logjam in conservative legislation.

Early in Mr. Trump’s tenure, some Senate Republicans said a change in the filibuster rules on legislation remained a possibility if Democrats refused to give any ground to the unified Republican government. But the shaky start of the Trump administration and the ensuing chaos seem to have left Republicans on Capitol Hill less inclined to take big political risks for the president.

The certainty of the sentiment against a change was striking.

“He can say what he wants,” Mr. Flake said of Mr. Trump. “This is separation of powers. We appropriate.”

Mr. McConnell, who considers himself an ardent Senate institutionalist, was always reluctant to endorse such a radical departure from Senate tradition, and he said so repeatedly. He did, however, engineer a change that allowed Republicans to break a filibuster against Neil M. Gorsuch with a simple majority vote and put him on the Supreme Court last month.