But less than a year ago, some of the same Democratic politicians who are now attacking Trump for firing Comey called for the director's resignation or questioned his credibility.
The White House has taken notice of the Democrats' prior statements and used them to defend the president's decision.
"They want to come out, they want to talk about all of these — they love Comey and how great he was," deputy press secretary Sarah Huckabee Sanders said during Thursday's White House press briefing. "Look at the facts. The facts don't lie. Their statements are all right there."
Here are some criticisms of Comey by Democrats (and one independent) before he was fired:
Senate Minority Leader Chuck Schumer of New York
"I do not have confidence in him any longer," Schumer told Bloomberg on Nov. 2.
"To restore my faith, I am going to have to sit down and talk to him and get an explanation for why he did this," he added.
House Minority Leader Nancy Pelosi of California
"Maybe he's not in the right job," she said to CNN on Nov. 2. "I think that we have to just get through this election and just see what the casualties are along the way."
Pelosi continued that Comey's letter to Congress about the review of Clinton's emails was a "mistake."
Former Sen. Harry Reid of Nevada
In October, Reid suggested Comey's actions "demonstrated a disturbing double standard for the treatment of sensitive information" and may have violated "the Hatch Act, which bars FBI officials from using their official authority to influence an election," in a letter to the director.
Reid wrote that he has "been a supporter" of Comey's and "led the fight" to get him confirmed, as he believed Comey was a "principled public servant."
"With the deepest regret, I now see that I was wrong," Reid added.
Sen. Bernie Sanders, I-Vt.
Sanders told ABC News just before Trump's inauguration that it "would not be a bad thing for the American people" if Comey stepped down.
"I think that Comey acted in an outrageous way during the campaign," said Sanders. "No one can say that this was decisive or this is what elected Trump, but clearly his behavior during the campaign in terms of what he said during the week or two before the election was unacceptable."
At the time, Sanders decried that there was no investigation into possible collusion between Russia and the Trump campaign, a situation that has changed.
Rep. Steve Cohen of Tennessee
In October, Cohen called on Comey to "resign his position effective immediately."
"If Director Comey cares about the bureau and the rule of law … I'm sure upon reflection of this action, he will submit his letter of resignation for the nation's good," Cohen wrote.
He bashed Comey's letter as "plainly premature, careless and unprecedented."
On Tuesday, after Comey's firing, Cohen said in a statement that he earlier hoped Comey would receive the Profiles in Courage Award for his Russia investigation.
Rep. Jerry Nadler of New York
"The president can fire him for cause and ought to. He violated all the guidelines and put his thumb on the scale of an election. Whether it was decisive or not is a different question," Nadler told CNN on Nov. 14.
Rep. Maxine Waters of California
"All I can tell you is the FBI director has no credibility. That's it," Waters told reporters after leaving a Jan. 13 classified briefing on Russia's meddling in the 2016 election.
In an interview with MSNBC on Wednesday, she argued that Trump should not have fired Comey in the middle of the Russia probe and as a result "basically has interfered with an investigation where he may be implicated."
Waters added, "If [Clinton] had won the White House, I believe that, given what he did to her and what he tried to do, she should have fired him."
Rep. Hank Johnson of Georgia
"My confidence in the FBI director's ability to lead this agency has been shaken," said Johnson, after the Jan. 13 closed-door briefing on the Russia investigation for House members.
In a statement released Wednesday, he called Comey's firing "unwarranted" and argued it "suggests an attempt to squelch an investigation in an effort to cover up wrongdoing."
Rep. Debbie Wasserman Schultz of Florida
"I think Director Comey has taken enough actions that call into question his ability to continue to serve credibly," she said during a CNN appearance on Jan. 17. "I would lean in the direction that he no longer is able to serve in a neutral and credible way."
After Comey's firing, Wasserman Schultz, a former chairwoman of the Democratic National Committee, said that it was "a dark day for justice in America."
"The conduct of FBI Director James Comey before the 2016 election was certainly disturbing and undoubtedly deserved criticism and scrutiny," she said in a statement. "But the reasoning and timing behind this firing is absolutely preposterous and unbelievable."