President Donald Trump on Sunday doubled down on criticizing House Oversight Committee Chairman Elijah Cummings, D-Md., and his Baltimore-area congressional district.

"Congressman Elijah Cummings has done a very poor job for his district and the City of Baltimore," he tweeted on Sunday, claiming that the congressman has "failed badly." Later Sunday, Trump called Cummings, who is black, a "racist."

"If racist Elijah Cummings would focus more of his energy on helping the good people of his district, and Baltimore itself, perhaps progress could be made in fixing the mess that he has helped to create over many years of incompetent leadership," Trump tweeted. "His radical 'oversight' is a joke!"

Sunday's outburst came after a day of heated rhetoric from the president lobbed at Cummings. Early Saturday, Trump referred to Cummings' district as "a disgusting, rat and rodent infested mess" and said that "no human being would want to live there."

Trump continued his attacks throughout Saturday, tweeting later that night, "Statistically, Baltimore ranks last in almost every major category." It was not clear what set of statistics Trump was referencing.

Top Democrats as well as prominent Baltimoreans swiftly rebuked Trump's comments as "racist," "disgraceful," and "dangerous." Trump on Sunday responded to criticism of his comments by accusing Democrats of playing the "race card."

"There is nothing racist in stating plainly what most people already know, that Elijah Cummings has done a terrible job for the people of his district, and of Baltimore itself," Trump tweeted Sunday afternoon. "Dems always play the race card when they are unable to win with facts. Shame!"

Democrats blasted the presidents remarks on the Sunday shows. On CNN's "State of the Union," Rep. Rashida Tlaib, D-Mich., who herself has come under the president's ire, said Trump "has a hate agenda."

"He doesn’t have a policy agenda and that’s what he falls down on,” Tlaib said.

Sen. Bernie Sanders, a 2020 presidential contender, told "State of the Union" that "it's unbelievable that we have a President of the United States who attacks American cities, who attacks Americans."

"That is a disgrace," he added.

It's not just Democrats who have been critical of the president's attacks. Former New Jersey Gov. Chris Christie, a longtime Trump ally, said during an appearance on ABC's "This Week" that he thought Trump's tweets were "a bad idea." Rep. Will Hurd, R-Texas, told the show: "I wouldn’t be tweeting this way."

Meanwhile, acting White House chief of staff Mick Mulvaney defended Trump during a terse interview with "Fox News Sunday." Mulvaney said Trump was right to attack Cummings, who has been highly critical of acting Homeland Security Secretary Kevin McAleenan and his department's handling of migrants on the U.S. southern border. Mulvaney added that he would "get fired" as a congressman if his district had poverty like Baltimore, adding that Trump's tweets have "absolutely zero to do with race."

According to the U.S. Census Bureau, Cummings' district has a poverty rate of 16.6 percent. South Carolina's 5th Congressional District — where Mulvaney used to serve in Congress — has a similar poverty rate of 14.9 percent. Cummings' district also has a higher median household income than Mulvaney's former district.

In an appearance on CBS's "Face the Nation," Mulvaney said "I understand why" Trump's tweet is being seen as racist, “but that doesn’t mean that it’s racist." He added "everything that Donald Trump says is offensive to some people."

Cummings himself responded to the president's barbs on Saturday, tweeting that he is in his district every day.

"Each morning, I wake up, and I go and fight for my neighbors," Cummings said. "It is my constitutional duty to conduct oversight of the Executive Branch. But, it is my moral duty to fight for my constituents."

And Republican Lt. Gov. Boyd Rutherford tweeted: "Mr. President, @realDonaldTrump, I have substantial policy differences with Congressman @RepCummings. However, I hope your criticism is not directed at the many good and hard working people who live in the district."

The blowback extended to the city's largest publication, The Baltimore Sun, where a columnist labeled the president's tweets as "racist" and "hateful" while the publication's editorial board wrote a widely circulated editorial under the headline: "Better to have a few rats than to be one."

Well into Sunday, the hashtag #WeAreBaltimore was trending on Twitter. And in a viral clip from Saturday, Baltimore native Victor Blackwell, a CNN anchor, became visibly emotional on air while addressing the attacks.

The altercation comes just days after Cummings' committee voted to subpoena personal emails and texts of top White House aides, including Trump's daughter Ivanka Trump and her husband Jared Kushner, who are both prominent White House staffers. It also followed a press conference after former special counsel Robert Mueller's congressional testimony in which Cummings said he is "begging the American people to pay attention to what is going on" regarding the president and his associates.

"How can he get it done when he just wants to use his Oversight Committee to hurt innocent people and divide our Country!" Trump wrote Sunday.

Trump's Cummings rant echoes attacks he made about a group of four freshman lawmakers known as "The Squad" earlier this month. He set off a political firestorm after he tweeted that the four lawmakers, Tlaib as well as Reps. Ayanna Pressley, D-Mass., Alexandria Ocasio-Cortez, D-N.Y., and Ilhan Omar, D-Minn. should "go back" to where they came from instead of criticizing his administration.

All four are U.S. citizens and only one, Omar, was born outside of the U.S.

Cummings told "This Week" earlier in the month that he had "no doubt" that Trump is a racist.