WASHINGTON, D.C. — House Minority Leader Nancy Pelosi is scrambling to shore up the support she needs to become speaker again when Democrats take control of the chamber, but a prominent defector said he has the votes to prevent her from regaining the gavel.

Rep. Seth Moulton, D-Mass., who has long opposed Pelosi’s returning to the speakership, says he has enough firm commitments from fellow party members that he could defeat the California lawmaker in a floor vote.

“One hundred percent,” he said. “We’re getting more all the time, but we have enough.”

Moulton wouldn’t say exactly how many votes he has in his pocket or identify the members.

Pelosi has faced rebellion in the Democratic ranks before and always managed to emerge on top. But this time the struggle could be more difficult.

According to a tally of public comments, 11 newly elected members have pledged to vote against Pelosi in the speaker’s race, which will be decided as the first vote in the new Congress in January. Some have made ironclad promises to oppose her under “any circumstances” and others have made less strident promises. Another dozen incumbents are expected to vote no, according to public statements and sources whipping against Pelosi.

But it is unclear whether that opposition will hold and if it is actually enough to deny her the speakership.

Moulton is one of several lawmakers gathering signatures on a letter that he hopes will convince Pelosi to step aside and allow new Democrats to assume leadership roles. No one has announced that they plan to run against her and Pelosi has showed no sign that she is ready to step down.

Rep. Marcia Fudge, D-Ohio, said she is considering challenging Pelosi. “When you look at the people who support this party the most, they are women and African-Americans and especially African-American women,” Fudge told the Cleveland Plain Dealer. “We have to not just talk the talk, but walk the walk.”

Moulton said he plans to release the letter before a Nov. 28 closed-door Democratic meeting where the party will select the person they plan to put forward as speaker on the House floor.

“The whole point of the letter is to accelerate the process so it doesn’t spill out onto the floor,” Moulton said, suggesting he doesn’t want Democrats to be embarrassed by losing a vote live on television. “She’s the one who is trying to drive this to a floor vote. We want to make it clear before it comes to that that she should step aside.”

Pelosi has expressed confidence that she will win the vote. Her spokesman, Drew Hammill, reiterated that Wednesday.

“Leader Pelosi is very confident in her support among members and members-elect,” he said.

Pelosi allies have been whipping members to support her and have released letters outlining her fundraising and legislative prowess.

In the past 15 years, she has raised $728 million for Democratic members and in the last election cycle, she raised about half of the Democratic Congressional Campaign Committee’s spending.

Among those circulating letters of support: the head of EMILY’s List, a group that helps female candidates who support abortion rights and that backed the vast majority of the new female members; leaders of the health care group Protect Our Care; and the heads of several labor groups. Support has also come from fellow members who are expected to lead committees, including Reps. Elijah Cummings of Maryland, Richard Neal of Massachusetts, Nydia Velazquez of New York and Eliot Engel of New York.

Supporters argue that Pelosi has more than proven herself an effective leader and is ready to stand up to President Donald Trump or Senate Majority Leader Mitch McConnell.

“We’ve got a battle-tested leader at the top and I’m hoping that she will absolutely win,” said Rep. Jan Schakowsky, D-Ill., a close Pelosi ally. “She’s been in the room where it happens. She really understands, as one of the smartest strategists I’ve ever seen —even in the minority she has managed to run circles around the Republicans.”

“The question is,” Schakowsky said, “will some minority of the Democratic caucus try to sideline her on the floor, which I think will be very destructive.”

Publicly rebuking Pelosi could have significant consequences if she does ultimately win the speakership. She will help determine committee assignments and which bills get to the floor, among other decisions that could make life easier or more difficult for freshman members.

Pelosi has strategies in her arsenal as she pursues the majority votes she will need on the House floor. There are 435 members of the House; if all races are decided and every member votes, she’ll need 218 in her favor.