Democrats, Converted to Filibuster Foes, Are Set to Force the Issue

“The reality is that when you have a system that is not working effectively — and I would think that most would agree that the Senate is not a particularly well-oiled machine, right? — the way to fix that is to change the behavior,” she said. “Not to eliminate the rules or change the rules, but to change the behavior.”

Her remarks drew sharp criticism from progressive activists who said the senator was naïve to believe that Republicans would willingly alter their behavior when the filibuster has been so beneficial to them.

Other Democrats, though more quietly, remain apprehensive about changing the filibuster rules. But colleagues and activists believe they can be convinced to do so when it becomes clear that the future of minority voting rights across the country is on the line and that the party’s aggressive agenda is going to be stymied almost single-handedly by Mr. McConnell. Mr. Reid used private party meetings to build momentum for a change, and Mr. Schumer is following the same path.

Still, even some vocal proponents of gutting the filibuster are privately pessimistic about their prospects and fear that any gains made in June could quickly dissipate if the Senate spends July on infrastructure measures and then decamps, as scheduled, for the remainder of the summer.

Democratic senators and key aides say they believe they have made progress nudging senators like Jon Tester of Montana and Angus King of Maine, who are wary of changing the rules, toward doing so for voting-related bills, if not permanently. But at the same time, Mr. Manchin and Ms. Sinema have proved less pliable than they had hoped. And with outside groups ready to pour millions of dollars into ads in West Virginia and Arizona to ratchet up pressure, some Democrats fear that approach will only harden their stances.

Mr. Schumer, in his letter, warned that “the next few weeks will be hard and will test our resolve as a Congress and a conference.”

Whatever the outcome, Democrats say they are now headed for a climactic moment.

“It is all building toward a showdown on voting rights, and voting rights are the precondition to every other issue being considered fairly in our country,” Mr. Markey said. “I do believe a historical moment is about to arrive by the end of June on the Senate floor.”

Nicholas Fandos contributed reporting.