Rep. Thomas Massie (R-Ky.) announced Tuesday he will co-sponsor a resolution to oust Speaker Mike Johnson (R-La.) from the House’s top job.

Massie told his colleagues during a closed-door conference meeting that he will co-sponsor the motion to vacate resolution filed late last month by Rep. Marjorie Taylor Greene (R-Ga.), according to three GOP lawmakers in the room, becoming the first lawmaker to publicly join Greene’s effort.

Massie’s announcement came less than 24 hours after Johnson unveiled the outline of a plan to move foreign aid through the House, which includes voting on three separate bills to send assistance to Ukraine, Israel and Taiwan and a fourth measure that pertains to other national security priorities.

But in a departure from his previous positions, Johnson did not include border security provisions in the plan after months of Republicans — including the Speaker — demanding that any aid for Ukraine be paired with legislation to address the situation at the southern border, sparking intense opposition among conservatives.

Speaking to reporters after Tuesday’s meeting, Massie referenced Johnson’s decision to put Ukraine aid on the floor — in addition to his handling of government funding and the reauthorization of the U.S.’s warrantless surveillance authority — to explain why he is now backing the ouster effort.

“There’s only one person right now who could stop us from going into what happened last fall, and that’s Mike Johnson,” Massie said, referring to the ouster of former Speaker Kevin McCarthy (R-Calif.) in October.

“He’s cleaning the barn, that’s obvious,” he continued. “He had three things to do: He wanted to do an omnibus that broke all the spending records, he wanted to do FISA without warrants, now he wants to do Ukraine. Those are the three things. There are people riding him like a horse here; they don’t care when the horse collapses — I do, because it’s gonna throw our conference into turmoil.”

The Kentucky Republican said he asked Johnson to resign from the Speakership during the closed-door conference meeting, which the Louisiana Republican declined to do.

Johnson responded to the growing ouster effort on Tuesday, calling it “absurd.”

“I am not resigning and it is, in my view, an absurd notion that someone would bring a vacate motion when we are simply here trying to do our jobs,” Johnson said at a press conference in the Capitol. “It is not helpful to the cause, it is not helpful to the country, it does not help the House Republicans advance our agenda which is in the best interest of the American people here — a secure border, sound governance — and it’s not helpful to the unity that we have in the body.”

Both Greene and Massie have declined to say when they might trigger a vote on the motion-to-vacate resolution, but the support from the pair of conservatives means Johnson will more than likely need Democratic support to remain Speaker if the issue comes to the floor.

Republicans can only afford to lose two GOP lawmakers on any party-line votes, as the House breakdown currently stands, an edge that will decrease to one after Rep. Mike Gallagher (R-Wis.) resigns at the end of the week.

Some Democrats in recent weeks have said they would protect Johnson if he puts Ukraine aid on the floor.

Many Democrats, however, are withholding comment on Johnson’s foreign aid plan until text of the legislation is released.

Massie told reporters Tuesday that Johnson will “lose more votes” than McCarthy did when eight Republicans and all Democrats voted to remove him from the top job.

“If it is called, there will be a lot of people who vote for it,” Massie said.

No other Republicans immediately expressed support for the ouster effort Tuesday, but some hard-liners declined to comment.

Rep. Chip Roy (R-Texas) said he’s “not gonna talk about that” when asked about the motion-to-vacate push, and Rep. Scott Perry (R-Pa.), the former chair of the House Freedom Caucus, said he hasn’t “said anything about it” when asked if he will support the ouster effort.

Other Republicans, however, sharply criticized the growing push, arguing that such a move would be harmful for the country.

“I respect Thomas, but I disagree with that,” Rep. Ralph Norman (R-S.C.), another hard-line conservative, said Tuesday. “The last thing this country needs is to throw a Speaker out, even though I disagree with what he’s done. He’s an honest man, we went through the renditions, y’all know, I wouldn’t put the country through that, so I’m against that.”

Rep. Dan Meuser (R-Pa.) called the motion “dead wrong,” and Rep. Troy Nehls (R-Texas) told reporters he “can’t support that,” contending that there is not a viable successor to Johnson in the GOP conference.

“If we’re gonna identify a problem with Mike Johnson, and I understand, but you have to have a solution. So who? Who we gonna put in there now? If it’s not him then who? Who can manage this conference?” Nehls asked. “There isn’t anybody in that room I just walked out of that can manage this conference.”

Rep. Garret Graves (R-La.) predicted to reporters that, if a vote was forced on the ouster resolution, it would fail on the floor.

“You have a loose affiliated coalition government at this point, you’re not going to get a majority of votes for any new person. And for that reason, I don’t think that folks are going to go through with it at this point,” Graves said.

“It’s not in our interest to do it. I don’t think that the painful scars that we went through for weeks last year, I think that they still are fresh in people’s minds,” he added. “And that is going to a major disincentive for folks to actually pull the trigger on a motion to vacate.”

Miranda Nazzaro contributed. Updated at 11:55 a.m. EDT