The Red Line at Gallery Place Metro station early morning on Wednesday, Jan. 17, 2018, in Washington, D.C. (Salwan Georges/The Washington Post)

The Washington region’s U.S. Senators have joined the growing chorus of calls for the Metro board to keep its Riders' Advisory Council, the only direct way for riders to provide input to the agency’s governing body.

U.S. Sens. Benjamin L. Cardin (D-Md), Chris Van Hollen (D-Md.), Mark R. Warner (D-Va.) and Tim Kaine (D-Va.) issued a letter Wednesday asking the board not to eliminate the council. The board is scheduled to vote Thursday whether to dissolve the 21-member panel. Board members have argued Metro could more effectively solicit rider input through an online survey community known as Amplify.

“At a time when WMATA is rebounding from years of deep safety and operational problems and rebuilding trust with riders, it is disappointing to see an effort that is interpreted as a lack of interest in public input,” the senators wrote. “We hope you will reconsider your position on this and not vote to terminate the Council.”

The board was widely expected to approve the plan when it was announced earlier this month, but pressure from Montgomery and Prince George’s County officials, universal opposition from the region’s House delegation and now the objection of its four senators has thrown the measure into question.

“We appreciate the need to evaluate the most productive means of facilitating public input,” the senators' letter reads. “If there is a need to restructure the channels through which WMATA receives feedback, that can be done without dissolving the primary entity through which the views of Metro riders can reach Metro leadership.”

The letter, organized by Van Hollen, comes on the heels of a similar call from Democratic Reps. Anthony G. Brown (Md.), Steny H. Hoyer (Md.), Gerald E. Connolly (Va.), Donald S. Beyer Jr. (Va), Jamie Raskin (Md) and John K. Delaney (D-Md.), along with D.C. Del. Eleanor Holmes Norton (D). Rep. Barbara Comstock (R-Va.) — who said she was not given an opportunity to sign the letter from her colleagues — also joined in opposing the RAC’s dissolution as she worked with the group’s leadership to swing the vote in its favor, according to her office.

The clarion calls against dissolving the council have set up a contentious vote for Thursday’s board meeting. Two of the board’s eight members, Christian Dorsey, who represents Virginia, and Michael Goldman, who represents Maryland, have said they support the RAC’s continued existence. Maryland officials believe the measure is subject to a jurisdictional veto, meaning it cannot pass if both board members from a single local jurisdiction — D.C., Virginia or Maryland — join in voting against it.

Metro board Chairman Jack Evans was defiant, however, arguing that the members of Congress should spend their time focused on the more critical issues facing the system. Where, he asked, was action by Congress on the expiring Passenger Rail Investment and Improvement Act, which provides Metro with $150 million a year?

“Talk about misplaced priorities,” he said. “PRIIA’s in doubt. Pensions are out of control. And these men and women are writing me about the RAC?”

Evans said he had been informed that Maryland may exercise its jurisdictional veto to block the move to dissolve the council. He took issue with the use of the veto on a matter he described as “minor, in the scheme of things.” (Evans has turned to the veto on matters others regarded as frivolous in the past; He and Corbett A. Price, for example, threatened to block a land transfer for Maryland’s light-rail Purple Line if board members vetoed a board restructuring favored by the other jurisdictions,.)

“You threaten a veto on the budget or something like that, something major, some major decision that’s going to affect your [position] negatively, not this,” Evans said. “Now, what are we going to do? I don’t know. If the votes aren’t there, then we won’t do it.”

Evans said the board’s move to eliminate the RAC followed concerns about its drain on Metro staff resources.

“It’s an organization that maybe was useful in 2005, but clearly in my time on the board has not been and takes up an enormous amount of resources,” he said. “And why would we keep that? And so why are these members in Congress interfering in what is clearly a Metro board issue?”

The RAC holds one public meeting a month at Metro headquarters and meetings are attended by the agency’s board secretary. Metro reduced its staff support of the group in 2016, saying its role was to provide " technical assistance and logistics.” The board secretary or another staff member also attends the RAC’s five committee meetings per month.

Board member Clarence C. Crawford, who also represents Maryland, could cast the deciding vote on the matter. He declined to say this week he intends to vote.

“I’ve seen the arguments; I’ve been contacted by members of the RAC, I understand what’s come out of the two counties, seen the letter from the members of Congress,” Crawford said in an interview this week. “We’ll just see on Thursday. I think things will take care of themselves.”

Crawford hinted at the potential for a compromise, though he declined to get into specifics. He pointed to a working document prepared by Dorsey and several alternates on the board, which looked at ways to make the RAC function more efficiently and better serve its purpose. The board began an operational review of the RAC earlier this year amid concerns it was straining staff resources and was ineffective at carrying out its goal of representing riders.

“I’m not prepared to say what will happen because I don’t know,” Crawford said. “I think we’ll come to a good closure.”