They also note that Democrats have embarked on filibusters of their own since losing the majority in 2014, like blocking consideration of a Zika public health package because of provisions added by the House, as well as a Pentagon spending bill.

“It’s an odd thing to say for a guy who is leading multiple filibusters at the moment,” Don Stewart, a spokesman for Senator Mitch McConnell, the Kentucky Republican and majority leader, said about Mr. Reid’s view. “Why doesn’t he start next week by ending the Democrats’ filibusters of anti-Zika funding, of veterans funding, of funding for our troops in the field?”

If Democrats were to take back the Senate, they would most likely have a narrow majority, so assembling the votes to curtail the filibuster is far from a certainty. Some Democrats, namely more senior and centrist members, might balk at such a fundamental change. But other Democrats elected in recent cycles have clamored for a crackdown on the filibuster.

Formal rules changes now require 67 votes, but Senate precedents can be changed with a simple majority vote, as Democrats did in 2013 with the nominations, effectively changing the procedure. That has become known as the nuclear option.

It is doubtful Democrats would act hastily to scale back the filibuster against legislation. Members of both parties have been leery of such a move because more frequent changes in party control means advocates of eliminating the filibuster can quickly find themselves wishing they had the power as members of the minority. Mr. McConnell has voiced strong reservations about such changes, viewing them as damaging to the institution.

A more likely scenario would be for Democrats to see if a pattern of Republican obstruction through filibuster emerged, giving them an opening to rally public support as well as to persuade reluctant senators.

Supreme Court nominations present their own challenges. Some Democrats in the Senate, particularly women, have been very reluctant to lose the ability to use the filibuster to block a nominee seen as a major threat to abortion rights. That was one reason nominations to the court were not included in the 2013 changes. But should Republicans decide to block a Supreme Court nominee early in a Clinton administration after refusing this year to take up the nomination of Merrick B. Garland, Democrats could be spurred to take extraordinary action.