Donald Trump lashed out at Rep. John Lewis on Saturday after the civil rights icon said he doesn't view Trump as a "legitimate president” — and the confrontation threatened to trigger a broader boycott of Trump’s inauguration by Democratic lawmakers already on the fence about attending.

Trump showed yet again that no one who crosses him — no matter how revered or respected, as Lewis is among both parties in Congress — will necessarily be spared his ire. Lewis was one of the top organizers of the 1963 March on Washington, and his skull was fractured by state troopers police on "Bloody Sunday," the civil rights protest in Selma, Alabama two years later.

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"Congressman John Lewis should spend more time on fixing and helping his district, which is in horrible shape and falling apart (not to......mention crime infested) rather than falsely complaining about the election results. All talk, talk, talk — no action or results. Sad!" Trump wrote in two tweets Saturday morning.

The tweets, two days before the federal holiday honoring Martin Luther King, came after Lewis questioned Trump's victory in the presidential race in a pre-taped "Meet the Press" interview that aired Friday on NBC.

“I think the Russians participated in helping this man get elected, and they helped destroy the candidacy of Hillary Clinton,” Lewis told host Chuck Todd. Lewis said he does not view the "president-elect as a legitimate president” and won't attend his inauguration.

The 76-year-old lawmaker also testified against Trump's pick for attorney general, Sen. Jeff Sessions (R-Ala.), who has faced long-running accusations of racism that he denies.

The back-and-forth between Trump and Lewis is the latest sign of partisan upheaval since Trump's victory. Some of the most heated criticism of the president-elect has come from African-American lawmakers.

Lewis joined a growing group of House Democrats who have declared they’ll be skipping the inauguration rather than sitting by as President Barack Obama transfers power to Trump. Eighteen lawmakers so far have said they will not attend.

"I stand with @repjohnlewis and I will not be attending the inauguration," Rep. Mark Takano (D-Calif.) tweeted on Saturday morning. The hashtag #StandWithJohnLewis cropped up elsewhere on Twitter.

Lewis’ office did not immediately respond to a request for comment, nor did Trump's transition team.

But a source involved in the transition said "no one around Trump would suggest it's a good idea to attack John Lewis on Twitter."

Trump is particularly aggrieved by any comment that questions the legitimacy of his election, the source said, who added that there often is not a larger strategy at work. He is "not going to change. And when you attack him he's going to hit back, whatever anyone thinks."

Trump’s attack follows the formula of his previous response to slights on the campaign trail, including questioning Sen. John McCain’s war record. The president-elect even went after the Pope once.

His target this time provoked a sharp response from Democrats as well as one Republican senator.

Sen. Ben Sasse (R-Neb.), a fervent Trump critic throughout the campaign, retweeted Trump, adding: "John Lewis and his 'talk' have changed the world." Sasse on Friday had pleaded with Lewis to attend the inauguration. “To John Lewis, one of my heroes: Please come to the Inauguration. It isn't about a man. It is a celebration of peaceful transfer of power,” Sasse tweeted.

Democrats were more unsparing.

Rep. Hakeem Jeffries (D-N.Y.), a member of the Congressional Black Caucus, said Trump's attack on Lewis "puts him in a very grave hole," and members are trying to decide what's next and whether it makes sense to attend the inauguration.

"You can guarantee this will cause people to organize with even greater intensity," he said. "This will make it even more likely that additional members skip the inauguration."

Jeffries said to expect Democrats to keep up the legitimacy attack on Trump and that members of the Congressional Black Caucus are likely to speak in the next 24 hours. "Trump won this election because of his help from Russia," he said.

House Minority Leader Nancy Pelosi (D-Calif.) tweeted that "many have tried to silence @repjohnlewis over the years. All have failed."

Mike DuHaime, Chris Christie's top strategist who is close to many in Trump's orbit, said that while Lewis' moral status doesn't "make him immune from criticism or disagreement in the political arena, he has earned tremendous deference and respect. While Rep. Lewis's comments questioning the legitimacy of the election are wrong, any protracted disagreement with him, especially when it sounds personal, is counterproductive at a time when we should be trying our best to come together."

Ahead of #MLKday2017, let us remember that many have tried to silence @repjohnlewis over the years. All have failed.

— Nancy Pelosi (@NancyPelosi) January 14, 2017

Despite the backlash, Trump reiterated his position in another tweet Saturday night. "Congressman John Lewis should finally focus on the burning and crime infested inner-cities of the U.S. I can use all the help I can get!" he wrote.

While Lewis's district includes some poorer stretches of Atlanta and lags the national average on some key indicators, it is not a leader of poverty-ridden, crime-infested areas Trump that made it out to be and has a number of wealthy suburbs.

Lewis and the Democratic Party on Saturday sent out a fundraising email citing Trump's tweets.

Douglas Brinkley, a presidential historian at Rice University who met recently with Trump, said the president-elect is entering the White House with less goodwill than past presidents, according to many polls.

Brinkley said "the constant fights and controversies" is likely to shrink his political capital and that Trump needed to try to strike a more balanced tone.

"He's got a very divided country and hasn't been working particularly hard at healing that gaping wound," Brinkley said.

But whether the attack on Lewis damages Trump is unclear. Ari Fleischer, the former press secretary to President George. W. Bush, said Trump made many comments on the campaign trail that were thought to be the end of him.

"Politicians learn to stop saying anything controversial because their threshold of pain is low," Fleischer said. "Trump can be boorish, he can be offensive, he can be highly controversial, but he lets it rip, and people see him as not another politician who parses his lips like politicians are supposed to."