Centrist members in both parties held behind-the-scenes negotiations in hopes of avoiding that confrontation. But no deal came together, and Republicans went on to curb the filibuster and seat Mr. Gorsuch.

Now, as the Senate faces another court vacancy — one that could tilt the court’s ideological balance and cement a conservative majority — the Democrats have few tools to fight the nomination. A different outcome last year could have had a huge effect on the more consequential battle now taking shape.

Had Democrats retained the power to block President Trump’s choice of Judge Brett M. Kavanaugh, he might have been forced to find a more consensus candidate. With the Republicans’ Senate majority smaller than it was in 2017, Senator Mitch McConnell, Republican of Kentucky and the majority leader, might not have found it as easy now to corral the votes to overrule a filibuster. The entire political atmosphere around the nomination would be transformed.

“I never understood the strategy,” Mr. Bennet said about the insistence by leading Democrats and their activist allies that the party must try to derail Mr. Gorsuch with a filibuster even though the chances of success were slight to nonexistent. “We achieved nothing by filibustering Judge Gorsuch except giving Mitch McConnell the opportunity to strip us of our ability to filibuster a nominee who will cause a dramatic shift in the balance of the court.”

Escalating clashes over judges have torn the Senate apart for years. The tension over Mr. Gorsuch was the culmination of a series of brutal partisan episodes. In 2013, Senate Democrats used a procedural maneuver to end Republican filibusters against a series of lower-court judicial nominations made by President Barack Obama. Then, in 2016, Mr. McConnell and Senate Republicans refused to have so much as a hearing on Mr. Obama’s nomination in March of Merrick B. Garland to the Supreme Court.