For months, Republicans on Capitol Hill have stood by President Donald Trump despite damaging revelations surrounding the Russia investigation.

There was an incendiary dossier, the firing of a top adviser, and this week, reports that Trump asked FBI Director James Comey to end the investigation into his associate Michael Flynn. Then, on Wednesday evening, the Justice Department announced it was appointing a special counsel to investigate possible ties between Trump associates and Russia.

Two questions have loomed over the latest reports: Will Republicans turn against Trump? And if so, when?

Doubts about the President have grown among Republicans lawmakers. As the White House careens from one scandal to another, Republicans on Capitol Hill have become increasingly frustrated with their party’s leader, and in private, they say that are concerned that more serious revelations about wrongdoing by Trump will emerge.

“They are distraught by what he’s doing and continues to do,” Illinois Sen. Dick Durbin, the chamber’s second-ranking Democrat, said in an interview.

Recently, more Republicans have been willing to speak out publicly. Tennessee Republican Sen. Bob Corker said this week that the White House is in a “downward spiral,” and Arizona Republican Sen. John McCain said the White House revelations were reaching “Watergate size and scale.” Others have kept quiet or suggested that the President is the target of a determined campaign to undermine him.

At stake is nothing less than the Republican agenda in Congress. Some on Capitol Hill are even whispering about the viability of Trump’s presidency; a couple Republicans have joined Democrats in openly discussing impeachment.

After this week’s revelations, Republicans took an increasingly aggressive tack. Demands for Comey to testify are coming from all corners of Congress. Utah Rep. Jason Chaffetz, a conservative Republican and the chairman of the House Oversight Committee, was the first to officially request that the FBI turn over Comey’s memos of his conversations with Trump, and on Wednesday, he invited Comey to testify before the committee.

The Senate Intelligence Committee and the Senate Judiciary Committee have also both asked for the FBI to turn over Comey’s memos. The Intelligence Committee has renewed its invitation to have Comey brief its members.

And while Republican leaders have mostly avoided discussing Trump’s travails, House Speaker Paul Ryan said Wednesday that Congress “need[s] the facts.” Ryan supported Chaffetz’s request for more information about Comey’s claims from the FBI. It is the most intense activity surrounding the Russia investigation to date.

Still, many Republicans are not ready to fling themselves into opening new investigations into connections between Trump’s campaign and Russia.

When it comes to making major substantive steps toward intensifying the scrutiny into Trump, Republicans have chafed. On Wednesday, the House voted down an effort by Democrats to create an independent commission to investigate Russian interference in the 2016 election. Republicans had resisted calls for a special prosecutor to lead the investigation, arguing that the FBI should continue doing its work.

That’s because opposing the President is a difficult proposition for Republicans, who are loath to cross the leader of their party. The success of their agenda, from tax reform to health care, is closely tied to the success of the President. Polls show that the Republican base still stands firmly behind Trump. Crossing the voters who elected them is not a recipe for a GOP victory in 2018 congressional elections.

But the pressure on Republicans to break ranks is growing. And lawmakers are increasingly alarmed by the President’s words.

“As long as this continues, it’s hard to stand behind it. I’ll tell you in all honesty,” said Republican Rep. Mike Simpson of Idaho, where Trump won by more than 30 points. “Maybe there’s nothing there, but the problem is that [the White House] keeps stepping in it every day.”

“What we’re hearing is very concerning, very frightening,” Illinois Republican Rep. Adam Kinzinger told CNN. “I think the American people deserve answers.”

There have been muted calls of rebellion in Republican ranks: Michigan Rep. Justin Amash, a member of the arch-conservative House Freedom Caucus, told reporters on Wednesday morning that if Comey’s memo was true, it could merit impeachment proceedings.

Rep. Carlos Curbelo, a moderate Republican from Florida, said in a CNN interview on Tuesday night that “obstruction of justice” has “been considered an impeachable defense,” and he called on Comey to testify before Congress.

And across the Hill, Republicans in both the Senate and the House were virtually united in saying investigators should chase the new leads and talk to Comey.

“I wanna know what happened,” said South Carolina Republican Sen. Lindsey Graham, a member of the Judiciary Committee. “I’m not worried about political damage, I want to know what the Hell happened.”

Many rank-and-file Republicans are still marching faithfully behind the White House. Many of the more conservative members, particularly in the House, are deeply loyal to Trump, and know that keeping their jobs may depend on that.

“The memo itself in my mind would bear careful scrutiny to ascertain when it was written and why,” said Rep. Trent Franks, a conservative Republican from Arizona, casting doubt on Comey’s report.

Franks added he is a staunch Trump supporter. “I believe that fundamentally his commitment to America is real, and that his leadership is very, very important,” he said. “I’m inclined to do everything I can to support him, within the bounds of integrity.”

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