"Republicans should stand up to Comey and his tremendous corruption - from the fake Hillary Clinton investigation, to lying and leaking, to FISA abuse, and a list too long to name," Sanders said in a tweet on Monday night. "The President did the country a service by firing him and exposing him for the shameless fraud he is."
Sanders' comments follow Comey's roughly six-hour, closed-door interview with the House Judiciary and Oversight committee on Monday the second such hearing Comey is publicly known to have attended this month.
Comey, who was asked questions about the FBI's investigations into Russia's meddling in the 2016 presidential election and Hillary Clinton's emails, appeared to be distraught by Trump's repeated attacks on the department Comey once led until his abrupt firing in May 2017.
"Somebody has to stand up and speak for the FBI," Comey said to reporters after his testimony. "People who know better, including Republican members of this body, have to have the courage to stand up and speak the truth, not be cowed by mean tweets or fear of their base. There is a truth and they're not telling it. Their silence is shameful."
"The FBI's reputation has taken a big hit because the President of the United States has lied about it constantly," he added.
Clinton was investigated for mishandling classified information through her private email server during her tenure as secretary of state. The FBI concluded twice that it would not pursue criminal charges against Clinton.
A Justice Department investigation on Comey's handling of Clinton's email found that the former director had violated norms and damaged the department's reputation after announcing he would reopen the probe, days before the 2016 presidential election. But the inspector general also concluded his role in the investigation was not influenced by political bias.
Comey's appearance before Congress has touched a nerve among Republicans. Some members of the party have continued to express frustration about the Russia probe and have raised doubts about Comey's motivations.
Democrats have accused Republicans of staging a last-ditch effort to score political points before Democrats retake the House in 2019.
"I find it frustrating to be here answering questions about things that are far less important than the values this country is built upon," Comey said after the hearing.
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