President Donald Trump repeatedly went after Rep. Elijah Cummings (D-Maryland), the House Oversight Committee chairman, on Twitter over both days this weekend.

On Saturday and Sunday, Trump fired off 15 tweets about Cummings, one of many Democratic House leaders investigating him and his 2016 campaign, among other issues. The president went as far as calling Cummings “racist” and also blasted the House Oversight chairman for not doing enough to help his constituents in his Maryland district, which is mainly comprised of the greater Baltimore area and is made up of mostly black Americans.

“Someone please explain to Nancy Pelosi, who was recently called racist by those in her own party, that there is nothing wrong with bringing out the very obvious fact that Congressman Elijah Cummings has done a very poor job for his district and the City of Baltimore,” Trump began by tweeting on Sunday. Trump also called Baltimore a “rat and rodent infested” city.

He continued: “The Democrats always play the Race Card, when in fact they have done so little for our Nation’s great African American people. … Elijah Cummings has failed badly!”

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Trump went on to blast Democratic lawmakers, including Cummings and Pelosi, for not doing enough to fight crime and to improve living and working conditions in their districts. The president also rebuked Cummings for not helping to create more jobs for African-American voters, while boasting about his own record on black employment since taking office two years ago.

The attack on Cummings marks Trump’s latest of many on a minority Democratic lawmaker. Earlier this month, the president assailed four freshman female Congresswomen of color, telling them to “go back” to their countries of origin in a vitriolic series of tweets.

In an interview with Fox News on Sunday, acting White House chief of staff Mick Mulvaney said Trump’s latest tweets about Cummings were unrelated to racial issues but rather simply an effort to call out Cummings for his “lies” about the situation surrounding illegal immigrants at the Southern border and for his House panel’s investigations of Trump.

Fox News host Chris Wallace said he believed Trump’s comments about Cummings were an example of “the worst kind of racial stereotyping.”

“It has absolutely zero to do with race,” said Mulvaney.

Like Mulvaney, Sen. Rick Scott (R-Florida) blasted Cummings for his criticism of Border Patrol officials’ actions against migrants.

“Congressman Cummings has sat there and attacked our Border Patrol agents, all right?” Scott said on NBC’s “Meet the Press.” “This reminds me of what happened to soldiers coming back from Vietnam.”

Many political pundits also noted that some facts and statistics about Baltimore and Cummings’ district in general appeared to contradict Trump’s claims that it is a broken district. For example, the district has a higher per-capita income than the national average.

Cummings responded to Trump’s attack with a tweet of his own on Saturday.