Rep. Paul Gosar (R-Ariz.) announced Friday he is joining a motion to vacate against House Speaker Mike Johnson (R-La.), the third Republican to do so.

Why it matters: It's the latest salvo in a growing GOP rebellion against Johnson that threatens to topple his speakership unless Democrats come to his rescue.

• The move comes after the House advanced a foreign aid package with Democratic support.

What he's saying: "I have added my name in support of the motion to vacate the Speaker," Gosar said in a statement.

• Gosar cited the passage of the foreign aid bill, which includes aid to Ukraine that right-wing hardliners staunchly oppose, as well as Republicans' recent difficulty in passing border legislation.
• "We need a Speaker who puts America first rather than bending to the reckless demands of the warmongers, neo-cons and the military industrial complex making billions from a costly and endless war half a world away," he said.

State of play: Gosar joins Reps. Marjorie Taylor Greene (R-Ga.), who introduced the measure, and Thomas Massie (R-Ky.).

• Greene has said a vote to pass Ukraine aid would trigger the motion to vacate, but declined to take reporters' questions about timing on Friday.
• The package will be voted on Saturday thanks to Democrats taking several rare steps to help it overcome procedural hurdles that typically pass along party lines.

What we're hearing: Massie, in a brief Capitol Hill interview, suggested the motion is unlikely to be forced to a vote this week.

• "We want Mike Johnson to resign. We don't want to go speaker-less. So the goal is to show him, through co-sponsorship, how much support he's lost and hopefully he'll get the message and give us a notice so that we have time ... to replace him," Massie said.
• "There's a fourth and a fifth who are waiting as well" to co-sponsor the measure, Massie said.

Yes, but: Democrats have long suggested they would save Johnson after he put Ukraine aid on the floor.

Editor's note: This story is developing and will be updated.