Rep. Jim Bridenstine of Oklahoma — a conservative who voted for Ryan last year for speaker— is threatening to pull his support if the Wisconsin Republican won't fall in line behind the GOP nominee.
"Given the stakes of this election, if Paul Ryan isn't for Trump, then I'm not for Paul Ryan," Bridenstine tweeted Wednesday.
Other conservative Republicans have also flashed their anger toward Ryan over his position that he wouldn't defend or campaign with Trump, raising the specter that Bridenstine could be the first in a crowd of conservatives rebelling against the speaker.
The GOP has been gripped by infighting since a 2005 video surfaced last week showing Trump describing women in vulgar and sexually aggressive terms. Ryan hasn't withdrawn his endorsement of Trump but he did tell House Republicans Monday that he will no longer defend
the nominee and will devote the remainder of the campaign season to helping Republicans in House and Senate races.
Several angry GOP members on that call pushed back at Ryan, arguing he should continue to stand strongly behind Trump. Trump repeatedly blasted Ryan Tuesday, lamenting his leadership and blaming him for eroding party unity.
Yet on Wednesday, several of Trump's biggest supporters in the House Republican Conference privately urged the campaign in a private conference call to back away from the Ryan attacks and focus on Democrats instead, according to a source on the call.
Ryan's spokeswoman AshLee Strong said the speaker is "fighting to ensure we hold a strong majority next Congress, and he is always working to earn the respect and support of his colleagues."
After backing Ryan in 2015, Bridenstine noted in a statement that his support came with conditions.
"I will work constructively with the new Speaker to advance sound legislation addressing the nation's urgent needs, and I will also hold him accountable to lead House in responsibly performing its representational duties and advancing our national interests," he said at the time.
The simmering tension is significant because there will be another vote next month for speaker. Assuming the GOP keeps control of the House, the Republican Conference will select its choice for speaker in mid-November in a closed-door secret ballot election. The election requires a majority support to be nominated for speaker.
But the more politically treacherous vote is in January when the full House will choose its speaker. Since Democrats will vote for their own candidate, Ryan wouldn't be able to lose more than a handful of votes if the chamber is narrowly divided, as is expected. That means he would have to limit GOP defections in order to win the 218 votes needed to become speaker.
Ryan was already facing some pressure from some of his members on the right of the conference, many of whom have been critical he hasn't pushed hard enough for their legislative priorities. Some House conservatives have called on GOP leaders to move the date for leadership elections later, saying they don't want to vote for re-electing Ryan until they evaluate how he handles year-end spending negotiations. Asked about that request last month, Ryan said he expected the conference to vote at the same time it traditionally does after every election.
Last October, 10 House Republicans didn't vote for Ryan when the entire House took a roll call vote for the speaker.
Meanwhile, Trump campaign manager Kellyanne Conway held a conference call Wednesday with House Republicans who back the GOP nominee. The lawmakers urged Conway to tell Trump to focus his fire exclusively on Hillary Clinton — and not on his own party.
A source on the call said Conway acknowledged what they were saying about Ryan. But she did not commit one way or the other.