President Trump's bombshell decision to fire FBI Director James Comey Tuesday evening led to Democratic suspicions that Trump's real goal was to hamper the probe into his alleged ties to Russia, and revived demands for a special prosecutor to carry out that investigation.

Many Democrats were openly claiming it was a brazen Trump cover-up of historic proportions.

"Nixonian," protested Sen. Bob Casey, D-Pa. A Democrat in the House, Rep. John Conyers of Michigan, compared Comey's firing to the "Saturday Night Massacre" during Watergate and said it "places our nation on the verge of a constitutional crisis." Senate Minority Leader Chuck Schumer, D-N.Y., called it a "big mistake."

At a minimum, Trump's surprise move ensures that the confirmation hearings for Comey's successor will be dominated by Democratic questions about alleged collusion between the Russians and members of Trump's campaign team. But it could also breathe new life into a Russia probe that has up to this been point been stalled, and hampered by partisan fights and inconclusive unclassified evidence.

The White House said the president acted on the advice of Attorney General Jeff Sessions, who has recused himself from the Russia probe after failing to disclose meetings with the ambassador from Moscow during his confirmation hearings, and Deputy Attorney General Rod Rosenstein, the top Justice Department official for the investigation.

Rosenstein's memoranda recommending Comey's ouster emphasizing the former FBI director's handling of the Clinton email investigation, chiding his "gratuitous" publication of "derogatory information about the subject of a declined criminal prosecution," a not too thinly veiled reference to the former secretary of state and 2016 Democratic presidential nominee.

But Democrats were unconvinced, and saw the decision as one that would help insulate Trump from the ongoing investigation.

"The need for a special prosecutor is now crystal clear," Sen. Richard Blumenthal, D-Conn., in reaction to the news. "President Trump has catastrophically compromised the FBI's ongoing investigation of his own White House's ties to Russia."

Blumenthal and others found it unconvincing that Trump would fire Comey over his treatment of Clinton. Trump campaigned on the idea of prosecuting Clinton for her private email server, though he has abandoned that pledge since taking office, and his rallies often featured crowds chanting "lock her up."

Trump's own statement announcing the firing made no clear mention of Clinton or any other rationale for the change. He did, however, mention the Russia probe when he expressed gratitude to Comey for telling him "on three separate occasions" he is not under investigation.

Trump's decision also came after Monday's hearing on the Russia investigation, which seemed to open the door again to the idea that there may be some connection between Trump and Russia. Former National Intelligence Director James Clapper said that while he knew of no evidence of Trump-Russian collusion, he also was not aware of what was going on in the FBI investigation of these matters.

At the same hearings, former acting Attorney General Sally Yates, an Obama administration holdover, said former national security adviser Michael Flynn was "compromised" by the Russians and vulnerable to blackmail.

All this has Democrats, and even some Republicans, seeing a connection.

"I agree with every word of the Rosenstein memo," tweeted former Clinton spokesman Brian Fallon. "But in drafting it to provide a pretext for Comey firing, Rosenstein let himself be Trump's patsy."

In the meantime, the Trump administration spent Tuesday night reminding Democrats that they haven't been fans of Comey since late October, when he announced a re-opening of the investigation into Clinton's private emails.

"Cryin' Chuck Schumer stated recently, 'I do not have confidence in him (James Comey) any longer," Trump tweeted. "Then acts so indignant."