Rep. Maxine Waters, D-Calif., speculated Monday that if Martin Luther King Jr. were alive in 2018, he would take to the streets to march for President Trump's impeachment, much like he did to advocate for civil rights in the 1950s and '60s.

"If MLK was alive today, he'd be marching not only for civil rights & protecting voting rights, but to urge Members of Congress to accept their responsibility to save the U.S. from a dangerous man who has no respect for our Constitution & no concern for strengthening our democracy," Waters wrote on Twitter.

"Dr. Martin Luther King Jr. would have encouraged every responsible human being to march for justice, to march for peace, and most of all, to march for the impeachment of Donald Trump. #ThankYouMLK50," she added, with a hashtag marking 50 years since the civil rights icon was assassinated in Memphis, Tenn.

The California Democrat's high-profile criticism of Trump and her continued calls for his impeachment have prompted death threats from some of the president's self-identified supporters, as well as resulted in her being targeted by Russian bots online.

But her opposition to Trump has not diminished, despite the perceived personal and political risk.

On Friday, she called Trump "a racist and indecent man with no good values" in the wake of reports he had made disparaging remarks about Haiti and African nations in a White House meeting with senators to discuss immigration.