"Watching Senator Richard Blumenthal speak of Comey is a joke," Trump wrote on Twitter, attempting to divert attention to Blumenthal's military record.
"'Richie' devised one of the greatest military frauds in U.S. history," Trump tweeted. "For years, as a pol in Connecticut, Blumenthal would talk of his great bravery and conquests in Vietnam - except he was never there."
"When caught, he cried like a baby and begged for forgiveness...and now he is judge & jury. He should be the one who is investigated for his acts."
Trump previously tweeted about Blumenthal's military service in February
. The senator admitted in 2010 to misrepresenting his military service after saying he had been "in" Vietnam. Blumenthal served in the Marine Reserves in Washington, not Vietnam.
"I have misspoken about my service, and I regret that, and I take full responsibility," Blumenthal said in 2010.
Trump did not serve in the military and received several deferments during the Vietnam War, although Blumenthal has not been the only person whose military service he has scrutinized. He has also criticized Sen. John McCain
, who was a prisoner of war in Vietnam.
Democratic senators sharply criticized Trump's decision to fire Comey on Tuesday, with some calling for a special prosecutor to investigate Russian meddling into the 2016 US election and any connection to Trump's aides.
Blumenthal, speaking on CNN's "New Day" just before Trump tweeted, told Alisyn Camerota that "what we have now is really a looming constitutional crisis that is deadly serious because there is an investigation ongoing."
The Connecticut lawmaker compared Trump's actions to those that eventually led to the resignation of President Richard Nixon.
"Ultimately, there may be subpoenas to the President of the United States, just as occurred in 1973 precipitating 'United States v. Nixon' and the similar firing of a special prosecutor," Blumenthal said.
"So what's needed now is an independent counsel and special prosecutor."
Blumenthal wasn't the only person to draw comparisons between Trump's firing of Comey and Nixon's "Saturday Night Massacre,"
during which the former president ordered the firing of Watergate special prosecutor Archibald Cox. But Blumenthal was the only person to get a personal response from the President Wednesday morning.
Nixon, by the way, ordered the firing of Cox, but Attorney General Elliot Richardson and his deputy, William Ruckelshaus, refused rather than comply with the order. Cox was eventually fired by then-US Solicitor General Robert Bork.