(CNN) Republicans are moving fast to squelch Justin Amash's rebellion against Donald Trump before his conclusion that the President "engaged in impeachable conduct" -- the first by a GOP lawmaker -- can gather momentum.

But Democrats who want a more hardline strategy against the President are seizing on the Michigan congressman's sudden intervention to pile pressure on their own leaders for tougher action.

Amash's act of conscience on Saturday sparked immediate speculation over whether a tiny leak in the Republican dam could grow into a torrent of support running away from the President.

After all, it was a rising tide of Republican disgust that eventually became the unstoppable force that led to the resignation of President Richard Nixon in 1974.

The early signs are that Amash's protest will not materially shift political dynamics in Washington that mean any attempt to impeach Trump remains a long-shot scenario.

But it introduced an unpredictable dimension into the building political storm over potential House testimony by Robert Mueller as Democrats accuse Attorney General William Barr of slow rolling a decision on a date for the special counsel to appear.

Amash accused Barr of "deliberately" misrepresenting Mueller's report -- an explosive charge that will ensure Mueller will face an uncomfortable spotlight whenever he arrives on Capitol Hill -- for a hearing that now seems unlikely to occur before early June.

But a least a few more Democrats declared that his apostasy met the bipartisan test set by skeptical party leaders for initiating impeachment proceedings -- or at least toughening the strategy behind investigations already under way in committees.

"I think it's a watershed moment," Rep. Pramila Jayapal, D-Washington, said on CNN's "State of the Union."

"For weeks, Speaker Pelosi has saying this needs to be bipartisan if it's going to move forward just from the practical perspective of impeachment moving forward.

"And I think Justin Amash coming on board means that there is now bipartisan support for really understanding the seriousness of what is in the Mueller report."

But Democratic leaders in the House have long indicated that they would not seek to impeach Trump if his GOP firewall held in the Senate -- where a two-thirds majority would be needed to convict the President in an impeachment trial.

Even Utah Sen. Mitt Romney, who was dismayed by the Mueller report's catalog of furtive meetings between Trump aides and potential evidence of obstruction, stopped short of endorsing Amash

"My own view is that Justin Amash has reached a different conclusion than I have. I respect him, I think it's a courageous statement," Romney told CNN's Jake Tapper.

"The American people just aren't there," he added. "The Senate is certainly not there, either."

Had Amash been a member of the Senate, rather than one of 435 members of the House, his intervention would have been more significant. In order for Trump to be convicted after a House impeachment vote, Democrats must peel away an almost unthinkable group of 20 Republican senators to eject the President.

Romney admitted that he found Trump's dishonesty and misleading conduct revealed by Mueller "really, really troubling and unfortunate and distressing."

"But I believe that to make a case for obstruction of justice, you just don't have the elements that are evidenced in this document," the former GOP nominee said on "State of the Union."

Amash warned in a string of tweets Saturday that few members of Congress had even read the Mueller report that he said contained "multiple examples" of Trump's obstruction of justice.

"Contrary to Barr's portrayal, Mueller's report reveals that President Trump engaged in specific actions and a pattern of behavior that meet the threshold for impeachment," Amash wrote.

'No signs' impeachment can succeed: top Democrat

In another sign that Amash's impeachment call would not become a headache for Trump, a top House Democrat indicated that a broader GOP revolt would be needed to change the strategy.

"I think that what the Speaker has referred to and I have as well, is can an impeachment even be potentially successful in the Senate? We see no signs of that yet," Adam Schiff, who chairs the House Intelligence Committee, said on CBS "Face the Nation."

Schiff did however praise Amash for showing "more courage than any other Republican in the House or Senate."

He also signaled that impeachment could be moving closer — not because of Amash -- but owing to the administration's "maximum obstruction" of Democratic investigations.

Amash's call for impeachment predictably ignited an angry Republican backlash.

"Never a fan of @justinamash, a total lightweight who opposes me and some of our great Republican ideas and policies just for the sake of getting his name out there through controversy," Trump tweeted.

"Justin is a loser who sadly plays right into our opponents hands!"

Never a fan of @justinamash, a total lightweight who opposes me and some of our great Republican ideas and policies just for the sake of getting his name out there through controversy. If he actually read the biased Mueller Report, "composed" by 18 Angry Dems who hated Trump,.... — Donald J. Trump (@realDonaldTrump) May 19, 2019

Republican National Committee chair Ronna McDaniel accused Amash of "parroting the Democrats' talking points on Russia."

"The only people still fixated on the Russia collusion hoax are political foes of President Trump hoping to defeat him in 2020 by any desperate means possible," she wrote in a tweet.

House Republican leader Kevin McCarthy, a staunch Trump ally, questioned whether Amash was a genuine conservative.

"You've got to understand Justin Amash. He's been in Congress quite some time. I think he's asked one question in all the committees that he's been in," McCarthy said on Fox News.

"He votes more with Nancy Pelosi than he ever votes with me. It's a question whether he's even in our Republican conference as a whole."

According to the American Conservative Union, however, Amash had an 88% record of voting with the group's positions last year.

'Watershed moment'

Liberal Democrats who have been frustrated by House Speaker Nancy Pelosi's unwillingness to move toward impeachment seized on Amash's remarks.

Democratic Rep. Rashida Tlaib, called on her fellow Michigander to sign on to her effort to trigger an impeachment investigation.

"I've got an impeachment investigation resolution you're going to want to cosponsor," Tlaib tweeted.

Pelosi has been juggling the House's constitutional imperative to consider the President's conduct and the fervent disdain in which he is held by liberal grass roots activists with the knowledge that impeachment would open political schisms that could damage Democrats in 2020 if they are seen as overreaching.

"I think the President every day gives grounds for impeachment in terms of his obstruction of justice," Pelosi said on Thursday, condemning the White House for not complying with Democratic subpoenas.

"Now I don't want to impeach," adding, "I want them to give us the information before they have to spend too much money on lawyers," she added.