U.S. Rep. Matt Gaetz (R-FL) speaks during a rally hosted by FreedomWorks September 26, 2018 at the West Lawn of the Capitol in Washington, DC. Alex Wong | Getty Images

Rep. Matt Gaetz, R-Fla., one of President Donald Trump's most vocal and committed supporters in Congress, on Tuesday sent what appeared to be a threatening tweet to Trump's ex-lawyer, Michael Cohen, on the eve of his public testimony before Congress. "Hey @MichaelCohen212 - Do your wife & father-in-law know about your girlfriends?" Gaetz wrote in a since-deleted tweet Tuesday afternoon, while Cohen was still testifying behind closed doors before the Senate Intelligence Committee — the first of three days of congressional hearings.

"Maybe tonight would be a good time for that chat. I wonder if she'll remain faithful when you're in prison. She's about to learn a lot..." Gaetz wrote. Cohen's legal representative, Lanny Davis, said in a statement, "We will not respond to Mr. Gaetz's despicable lies and personal smears, except to say we trust that his colleagues in the House, both Republicans and Democrats, will repudiate his words and his conduct." Davis added: "I also trust that his constituents will not appreciate that their congressman has set a new low — which in today's political culture is hard to imagine as possible." Following Gaetz's tweet, House Speaker Nancy Pelosi on Tuesday posted a statement on Twitter to "encourage all Members to be mindful that comments made on social media or in the press can adversely affect the ability of House Committees to obtain the truthful and complete information necessary to fulfill their duties." Pelosi tweet: I encourage all Members to be mindful that comments made on social media or in the press can adversely affect the ability of House Committees to obtain the truthful and complete information necessary to fulfill their duties. Gaetz responded to Pelosi online, tweeting that while he wants to "create context around the testimony of liars like Michael Cohen," it "was NOT my intent to threaten, as some believe I did." "I'm deleting the tweet & I should have chosen words that better showed my intent. I'm sorry," Gaetz wrote.

Cohen is scheduled to speak for the first time in public testimony before the House Oversight Committee on Wednesday. The former longtime personal attorney and fixer for Trump, who pleaded guilty last year to campaign finance crimes, criminal tax evasion and lying to Congress, is also a central figure in special counsel Robert Mueller's probe of Russian meddling and possible Trump-campaign collusion during the 2016 presidential election. He is scheduled to begin a three-year prison term in May. A spokeswoman for the Oversight Committee declined CNBC's request for comment on Gaetz's tweet. Neither Gaetz's office nor representatives for Cohen immediately responded to CNBC's requests for a response to Gaetz's tweet. Shortly after the tweet was sent, Gaetz defended his message in remarks to reporters. "I think my tweet speaks for itself," Gaetz said. "This isn't witness tampering. This is witness testing." Gaetz denied that the tweet was a threat. "I don't threaten anybody. Michael Cohen threatens people," he said. "Michael Cohen is a PhD in threats and intimidation."