In the weeks since the Commerce Department announced plans to add a controversial question about citizenship to the 2020 Census, immigrant advocates have warned that it will depress the decennial count among noncitizens and their families, who may fear filling out the survey.

But a federal suit seeking to block the question aims to show how it would affect a broad swath of people — including U.S. citizens — living in areas such as Prince George’s County that have a high proportion of immigrants and minorities and are vulnerable to being undercounted.

Plaintiffs in the suit, which is backed by former U.S. attorney general Eric H. Holder Jr., include county residents such as Robyn Kravitz, whose 12-year-old son needs mental health services provided through Title 1 funds to schools with more low-income students; Nnabugwu Nwosu, who drives on congested local roads and sends his child to a Title 1-funded school; and Joanne Wilson, whose children don’t walk to school because there are no sidewalks, and who drives on roads riddled with potholes. Funding for Title 1 and transportation infrastructure is based on decennial census data.

The suit, filed last month in U.S. District Court for the District of Maryland, named these families as well as two plaintiffs in Arizona to illustrate how the services they receive through federal funding could be reduced if not enough people in their area fill out the 2020 Census. Last week, 12 more plaintiffs, including residents of Nevada, Texas and Florida, and two more in Prince George’s and Arizona, were added; all but one are U.S. citizens.

The lawsuit is being coordinated by the National Redistricting Foundation, a nonprofit organization affiliated with the National Democratic Redistricting Committee, which Holder chairs, and the plaintiffs are represented by the law firm Covington & Burling, where he is a partner.

The Justice Department requested in December that the Census Bureau add a citizenship question, which hasn’t appeared on the decennial count since 1950, though citizenship status is asked on smaller sample surveys. The Trump administration argued that getting an accurate count of the voting-eligible population through the census would help identify potential voting rights violations.

But in the weeks since Commerce Secretary Wilbur Ross announced that the question would be added, more than two dozen states and cities have sued to block it. Democratic lawmakers have requested that Justice produce documents to explain why and how the request came about, and lawmakers are expected to grill Census Bureau and Commerce Department officials at a public hearing on the question on Tuesday.

Opponents — among them six former census directors — contend that the question will reduce the response rate and lead to undercounts in areas with high numbers of immigrants. Both noncitizens, here illegally and legally, and citizens may fear repercussions if they fill out the survey, they say. If they fail to respond, states with significant immigrant populations, which are mostly controlled by Democrats, could lose seats in Congress, electoral college votes in presidential elections and federal funding based on census counts.

The lawsuit includes people in both red and blue states, to illustrate that they can all be negatively affected. It contends that the question goes against the constitutional requirement that the census count every person residing in the United States, including noncitizens. And it says the question could be devastating in places such as Prince George’s.

With a population that is 65 percent African American and 17.8 percent Latino, the county suffered a 2.3 percent undercount in the 2010 Census — the largest net undercount of any county in Maryland and one of the largest in the United States for counties of 100,000 or more residents.

That census counted 863,420 people in Prince George’s, and the bureau estimates that the county’s population has grown by 5.7 percent since then. But immigrants have expressed wariness about responding if the form includes a citizenship question, and a low-response rate on the 2020 count might not reflect the county’s growth.

That could mean services for Kravitz’s son get cut. She said one reason she and her husband purchased their home in the District Heights area of Prince George’s was because of the school services offered through Title 1 for their son Josh, 12, who has reactive attachment disorder. To avoid violent outbursts, he has an aide at school all day, paid for by the school.

If benefits disappear because the area is deemed to have too low a population to justify them, Kravitz fears that her son will be in danger of hurting himself or others.

“His condition can become a public safety hazard because of anger,” said Kravitz, who also has a 6-year-old daughter. “He needs a calm and predictable environment to get his needs served.”

It has already been hard to obtain services in the county. “It took eight months to find a therapist,” Kravitz said, adding that she suspects fewer therapists will choose to serve the area if the population count isn’t there to support them. “If funding gets cut, I’m going to lose the providers that can do this kind of care (and) it would be absolutely devastating to his mental health.”

At the same time, she understands the concerns voiced by immigrants in her tightly knit community. She is torn on how to advise them.

“One of the moms said, ‘I know they tell me that the census information is private, but I don’t know that there aren’t going to be ICE at my door in the morning,” she said, referring to immigration authorities. “I say, ‘I feel your fear, and I need you to fill out the paperwork because we need the funding.’ But as a friend, a neighbor, I totally think their fears are valid. And how can I ask them to sacrifice their kids’ safety to my kid’s safety?”

Prince George’s has already been the subject of litigation over the 2020 count. In late March it filed a lawsuit, along with the NAACP’s national headquarters and the organization’s Prince George’s branch, saying the government’s “deficient” preparation for the 2020 Census violates a constitutional mandate to count all the people in the country and disproportionately harms minorities.

Days later, Ross announced plans to add the citizenship question.

That was frustrating for Wilson, 43, another plaintiff in the Holder suit, who lives in Bowie. She would love for the county to build sidewalks in her neighborhood so her 7- and 10-year-old can walk to school. County roads she drives on to get to her job as a fundraiser for a nonprofit organization are full of potholes and have not been repaved in years. If federal funding to the county is reduced based on the census count, there will be less money for infrastructure projects at all levels, she said.

Wilson, a naturalized U.S. citizen from Trinidad, said many immigrants she knows do not plan to fill out the census if it includes a citizenship question, and she doesn’t blame them. The question, she says, has no business being in the decennial survey.

“My understanding of the census is it’s supposed to be a head count,” she said. “Whether you’re a citizen or not, you should have good roads to drive on . . . whether you’re a citizen or noncitizen, whether they’re from the state or passing through, why do we need to know that information?”

Nnabugwu Nwosu, 32, a small-business owner who lives in Hyattsville and drives along congested roads to get to work, said the question would be “very biased” against people living in his area. “It would make it look like certain places would not have as much population as others,” he said. “I’m sure it would have a major impact, whether it be on repairs or construction.”

Kravitz, too, worries that an undercount will reduce funding for roads and infrastructure. She and her husband already had to give up their electric car because there weren’t enough charging stations in the area; a charging-station company told them the population couldn’t sustain more.

Last week, she drove from her home to pick up her daughter, Ellie, from after-school gymnastics. It was 4:30 p.m. and the rush had begun; a line of stopped cars snaked ahead of her.

“This highway goes down to two lanes down here,” she said, adding that a request to expand it to three had recently been denied.

“They said there weren’t enough people using it.”