(FOX NEWS) -- As the third day of the ongoing impeachment trial of President Trump wrapped up in the Senate chamber, most of the drama was elsewhere -- with one witness for the Democrats accusing a Republican senator of "defamation" and "slander" after she questioned his patriotism and implicated him in a scheme to take down Trump from inside the White House.
The off-field spat began Thursday evening on Twitter, when Tennessee GOP Sen. Marsha Blackburn quoted the commanding officer of Lt. Col. Alexander Vindman as saying that Vindman was a "political activist in uniform."
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Vindman, a National Security Council official, testified during House Democrats' impeachment inquiry last year that Trump's Ukraine dealings left him in a state of "shock," and Democrats were quoting from Vindman's remarks during the Senate trial on Thursday. Vindman has denied knowing the identity of the whistleblower who flagged Trump's fateful July 25 phone call with Ukraine's president -- a claim that Republicans have questioned, because under cross-examination, Vindman apparently admitted to leaking the contents of Trump's call to the whistleblower.