President Trump criticized James Comey on Tuesday night, just hours before the FBI director testifies before the Senate Judiciary Committee.

Trump accused Comey of giving Hillary Clinton a “free pass” in the investigation into whether she mishandled classified information on her private email server.

It is unclear what exactly prompted Trump’s outburst, though it was likely a response to an interview Clinton gave earlier in the day in which she blamed several factors, including Russia, misogyny and Comey, for her November election loss to Trump.

Clinton blasted Comey for re-opening the FBI’s investigation into her emails in late October, just before the election.

“FBI Director Comey was the best thing that ever happened to Hillary Clinton in that he gave her a free pass for many bad deeds!” he tweeted Tuesday. “The phony Trump/Russia story was an excuse used by the Democrats as justification for losing the election. Perhaps Trump just ran a great campaign?”

Trump expressed measured confidence in Comey during an interview last month.

Asked by Fox Business Network’s Maria Bartiromo whether it was too late to fire Comey, Trump said it was not.

“No, it’s not too late, but, you know, I have confidence in him. We’ll see what happens. It’s going to be interesting,” Trump said. (RELATED: Trump Expresses Confidence In FBI Director But Says He Can Still Be Fired)

Comey, who was appointed to his 10-year term by President Obama in 2013, will be in the spotlight on Wednesday during his Senate Judiciary Committee testimony. In March, during his last appearance on Capitol Hill, Comey acknowledged for the first time that the FBI is investigating whether several Trump advisers cooperated with the Russian government during the campaign.

Iowa Sen. Chuck Grassley, the committee’s chairman, has already indicated that he plans to press Comey over the FBI’s arrangement with the former British spy who authored a dossier of research about Trump.

Grassley has written several letters to Comey asking about agreements that the FBI made with the ex-spy, Christopher Steele. Grassley has noted that Steele was working for an opposition research firm that was in turn working for an ally of Hillary Clinton’s. (RELATED: Grassley Presses Comey On ‘Material Inconsistencies’ In Trump Dossier Claims)

In a letter last week, Grassley told Comey that statements he has made about Steele’s dossier contain “material inconsistencies” compared to records he’s obtained from the Justice Department.

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