President Donald Trump on Tuesday called House Democrats’ impeachment a "lynching," employing a term associated with the extrajudicial killings of African-Americans while calling on Republicans to aid his political defense.

"So some day, if a Democrat becomes President and the Republicans win the House, even by a tiny margin, they can impeach the President, without due process or fairness or any legal rights. All Republicans must remember what they are witnessing here - a lynching. But we will WIN!" the President tweeted.

Trump has repeatedly railed against the probe, calling it a "witch hunt" and a "fraud," but Tuesday marks his first use of the term "lynching," which is associated with a period of horrific racial violence in the United States, in regard to the inquiry. Following Emancipation and the Civil War, killings, often carried out in public settings, known as lynchings, terrorized newly freed black Americans. Thousands of citizens were killed this way.

Trump's use of the term is also notable as he has frequently stoked racial tensions while in office, from referring to undocumented immigrants as an "infestation" tosharply criticizing African-American athletes who protest during the National Anthem.

White House deputy press secretary Hogan Gidley argued Tuesday that Trump's use of the word "lynching" to describe the impeachment process was fair.

Speaking to reporters, Gidley said Trump "is not comparing what happened to him with one of our darkest moments in American history. What he's explaining, clearly, is the way he's been treated by the media since he announced for President." He also claimed Trump was referring to the way Democrats were treating him, saying that the President is "receiving zero due process from Democrats on the Hill. That's what he's talking about."

Impeachment is a political process and the President, through the White House counsel, has opted not to cooperate and to instead block congressional requests.

The impeachment inquiry, which began four weeks ago, is moving rapidly, with ongoing witness testimony conducted on Capitol Hill and bombshell revelations opening up new avenues for investigation since the whistleblower's report about Trump's call with Ukrainian President Volodymyr Zelensky came under scrutiny. On Tuesday, the United States' top diplomat in Ukraine, acting Ambassador Bill Taylor,testifies behind closed doors. Though Democrats had hoped to hold a vote on impeachment before the Thanksgiving holiday, there is growing expectation that the votes could slip closer to the end of the year. Trump has lashed out against the investigation, questioning whether the whistleblower needs protection and slamming congressional Democrats.

Trump previously retweeted a statement during the 2016 election referring to his treatment by journalists as a "disgusting lynching" in September 2015.

CLARIFICATION: This story has been updated to reflect that Sen. Graham said the treatment of Trump is a lynching in "every" sense.

CNN's Manu Raju and Lauren Fox contributed to this report.