President Trump launched another broadside Saturday on a Democratic political opponent, calling a prominent black congressman’s Baltimore district a “disgusting, rat and rodent infested mess” and saying “no human being would want to live there.”

That Twitter attack on Rep. Elijah E. Cummings (D-Md.) plunged the nation into yet another anguished debate over the president’s divisive rhetoric. And it came just two weeks after Trump called out four minority congresswomen with a racist go-back-to-your-country taunt.

The assault on Cummings, chairman of the House Oversight and Reform Committee, prompted immediate condemnations from House Speaker Nancy Pelosi (D-Calif.), Baltimore Mayor Bernard C. Young and several other top Democrats.

The outburst also undercut efforts by many Republicans over the past two weeks to defend Trump and insist that his earlier attacks were based in ideology rather than race.

But Trump’s advisers had concluded after the previous tweets that the overall message sent by such attacks is good for the president among his political base — resonating strongly with the white working-class voters he needs to win reelection in 2020.

This has prompted them to find ways to fuse Trump’s nativist rhetoric with a love-it-or-leave-it appeal to patriotism ahead of the 2020 election, while seeking to avoid the overtly racist language the president used in his tweets about the four congresswomen.

It’s not clear whether Trump will abide by such limitations, however. The president kicked off his Twitter attack Saturday morning by calling the black lawmaker’s Baltimore district a “very dangerous & filthy place.”

Maryland’s 7th district, which Cummings has represented since 1996, includes about half of Baltimore City and has a median household income of around $60,000 and a higher percentage of college graduates than the country as a whole.

“Why is so much money sent to the Elijah Cummings district when it is considered the worst run and most dangerous anywhere in the United States,” Trump continued in another tweet. “No human being would want to live there. Where is all this money going? How much is stolen? Investigate this corrupt mess immediately!”

The attack on Cummings underscores Trump’s penchant for undermining any attempts by other Republicans to steer clear of overtly racial attacks.

As condemnations have poured in over the past two weeks accusing Trump of bigotry — including a bipartisan House resolution decrying his “go back” tweets as racist — Trump’s campaign has mounted an all-out effort to defend the president and turn his offensive comments into a political advantage with his base.

Republican officials say Trump is harnessing the anger of those who continue to feel left behind despite the strong economy, and steering their fury toward members of Congress he has accused of bad-mouthing the country and embracing socialist policies.

“This is Hillary’s ‘basket of deplorables’ all over again,” said Trump campaign communications director Tim Murtaugh, referring to a term Hillary Clinton used to brand some Trump supporters as bigots in 2016. “They’re trying to say anyone who supports this president is racist.”

Trump, who turned the “deplorables” label into a rallying cry for his base, is seeking to do the same in 2020 as he tries to retain support in key Midwestern swing states.

Trump kicked off the controversy with a July 14 Twitter attack on the four Democrats — Reps. Ilhan Omar (Minn.), Alexandria Ocasio-Cortez (N.Y.), Ayanna Pressley (Mass.) and Rashida Tlaib (Mich.) — suggesting that they “go back” to the “totally broken and crime infested places from which they came.” All four are U.S. citizens; Omar was born in Somalia.

That was followed several days later by a campaign rally in which the crowd broke into chants of “Send her back!” as Trump was attacking Omar. Facing some criticism from a smattering of Republican lawmakers, Trump briefly distanced himself from the chants — before fully embracing the chanters as “incredible patriots.”

Campaign advisers and party officials, some of whom spoke on the condition of anonymity to discuss internal deliberations, said that an appeal targeted at Trump’s white working-class base will not necessarily cost him moderate voters.

“The general assumption with everything Squad-related is this helps shore up our base. It definitely helps with white working-class voters,” said one person close to the campaign, using the term that refers to the four congresswomen. “I think that shows that this can be turned into a positive, in terms of a very political viewpoint.”

Publicly, campaign aides and advisers have sought to shift the conversation away from race and toward the less explosive territory of ideology. But they have also pushed back aggressively against charges of racism, seeking to make common cause with supporters who also feel they are too quickly branded as bigots.

Murtaugh said Democratic lawmakers are seeking to “create conditions where if you are a certain gender or a certain race all criticism is considered racist or sexist.”

Bryan Lanza, an adviser to Trump’s 2016 campaign and transition, said that although he did not like the “Send her back!” chants, he hoped Republicans would double down rather than back down from their attacks on the four lawmakers.

“Usually, when they are faced with charges of racism, Republicans hide a little bit. And the president’s not hiding,” he said. “And I think that’s what the Republican voters like about him.”

But there are also indications that Trump’s attacks on Democrats could cost him politically. In a Fox News poll released Wednesday, 63 percent of voters said Trump’s tweets attacking the lawmakers “crossed the line,” and 57 percent of voters said Trump does not respect racial minorities. And in an Economist/YouGov poll, 61 percent said it is “inappropriate” to tell a naturalized citizen to “go back to where you came from.”

Democrats running for president have increasingly sought to appeal to minority and moderate voters by highlighting the president’s divisive rhetoric.

“We have a president who is a racist,” Sen. Bernie Sanders (I-Vt.) said Wednesday at the annual convention of the NAACP. “A president who is trying to divide the American people up based on the color of their skin.”

At a news conference after the tweets were sent, Omar accused Trump of pursuing “the agenda of white nationalists.”

Trump has shown no sign of reversing course. A few days ago, he renewed his attacks on the four minority lawmakers, calling them “very Racist” and “not very smart.”

The president’s allies say that combative approach appeals to white Republicans who are tired of being accused of racism.

“Republicans, for as long as I can remember in politics, we’ve all been called racists just because of our policy ideas,” said Kelly Sadler, a spokeswoman at America First Action, a pro-Trump super PAC. “The Republicans who have been struggling with these criticisms want somebody to fight back. And the president now is reversing the game on the Democrats.”

Republicans are funding an opposition research campaign targeting the four lawmakers, and the Trump campaign has been disseminating talking points highlighting their controversial statements and liberal policies.

But some Republicans have expressed concern with how quickly Trump’s attacks escalated into racially offensive chants calling for Omar to be deported to Somalia.

“Sometimes crowds get a little unruly at times,” said Mark Jefferson, executive director of the Wisconsin Republican Party, referring to the “Send her back!” chants at the Trump rally in Greenville, N.C. “That’s not something that I feel terribly comfortable with. You won’t see me saying it.”

Jefferson said that although Trump performed better than expected in some rural parts of Wisconsin, he performed worse than the state’s Republican senator among suburban voters and establishment Republicans.

Some Republican moderates have warned that Trump’s red-meat attacks and divisive rhetoric could turn off those voters, but party leaders point to polls showing Ocasio-Cortez and other liberal lawmakers as toxic among Republican voters.

“The socialist squad is radically out of touch with mainstream America,” said Richard Walters, chief of staff of the Republican National Committee. “They turn off a vast swath of voters, from the most die-hard Trump supporter in rural Florida to a moderate voter in suburban Minneapolis.”

Andy Surabian, a Republican strategist and former White House official, said that even if Trump’s rhetoric offends some suburban voters, they will still vote for him rather than siding with Democrats.

“He can excite his base without alienating suburbia to the point where they’re not voting for him,” he said. “That’s what a coalition is. Not everyone agrees with everything.”

Trump can focus on appealing to his base of white working-class voters in part because his coalition may not need to deliver a popular vote victory for him to win the electoral college in 2020, said Dave Wasserman, a political analyst with the Cook Political Report.

“He may only need to come within 4 percent,” Wasserman said, adding that Trump’s rhetoric may boost his support among white voters in Michigan, Wisconsin and Pennsylvania. “The best way to come within 4 percent is to keep your core supporters motivated to turn out, especially in the upper Midwest.”

Democrats are banking on the idea that even if Trump’s language excites his base, it is likely to offend a diverse coalition of voters who will turn out to defeat him.

“I don’t think it’s going to depress Democrats. I think it’s going to make them angry,” said Jennifer Palmieri, an adviser to Clinton’s 2016 campaign.

Brian Schaffner, a political science professor at Tufts University, said a review of exit polling data from 2016 does not give a clear sense of what effect Trump’s amplified appeal to white working-class voters will have in 2020.

“We can’t really know for sure from our data whether the white grievance rhetoric is going to mobilize more support for Trump in 2020,” he said. “And it’s very possible that he may mobilize just as many — or maybe even more — opponents with this rhetoric.”

Michael Scherer and Colby Itkowitz contributed to this report.