Trump said in a tweet that the impeachment inquiry was being conducted "without due process or fairness or any legal rights."
"All Republicans must remember what they are witnessing here - a lynching," he wrote. "But we will WIN!"
Trump has previously used incendiary, racist remarks — opening up a deep racial wound and exposing it to the country’s sharp political divisions — as a way to pit Americans against each other and change the conversation from something he doesn't like.
In Tuesday's case, he was drawing attention away from the impeachment inquiry and the mounting evidence that he withheld aid from a foreign country to advance his personal political agenda.
His tweet sparked swift condemnation from Democratic lawmakers — and a few Republicans — while the White House later defended the president, saying he "has used many words to describe the way he has been treated" by the press.
House Speaker Nancy Pelosi announced in September a formal investigation into whether Trump tried to withhold aid to Ukraine in exchange for dirt on former vice president Joe Biden, one of the 2020 Democratic frontrunners.
But Trump's use of the word "lynching," calling upon a not-so-distant past when black people were terrorized, hung from trees, and killed by white mobs, appeared to be the most inflammatory rhetoric he's used to malign the impeachment inquiry.
According to the NAACP, there were 4,743 documented lynchings in the United States from 1882–1968. White people, in many cases threatened by the rise of black towns in the South after the end of slavery, conducted lynchings in public under the guise of protecting white women, then posed with the bodies of black people they killed and distributed body parts to the crowd.
Democrats, including several of the 2020 presidential candidates, have condemned Trump's comments.
Several Republican lawmakers, however, have defended the president. When asked by a reporter whether Trump's tweet was appropriate, Rep. Jim Jordan replied, "The president's frustrated." Sen. Lindsey Graham also echoed the president's remarks, calling the impeachment inquiry "a lynching in every sense."
Hogan Gidley, the White House deputy press secretary, told reporters hours after the tweet was posted that Trump wasn't comparing what's happening to him with "one of the darkest moments" in the country's history.
"He has used many words to describe the way he has been treated" by the press, Gidley said.
Some Republicans criticized the remark. Rep. Kevin McCarthy, the leading House Republican, said, "That's not the language I would use."
Sen. Susan Collins said it "brings back images of a terrible time in our nation’s history."
And Rep. Adam Kinzinger, a Republican from Illinois, called for Trump to "retract" the comment.