U.S. Commerce Secretary Wilbur Ross announced plans last week to add a citizenship question to the 2020 count. (Saul Loeb/AFP/Getty Images)

The District, Virginia, Maryland and 15 states filed a lawsuit Tuesday to block the Trump administration from adding a last-minute citizenship question to the 2020 decennial Census.

The suit, filed in the U.S. District Court for the Southern District of New York, also includes six cities and the bipartisan U.S. Conference of Mayors and comes a week after California sued the administration over the same issue.

Commerce Secretary Wilbur Ross announced the addition of the question last week, triggering outcry from census experts, immigrant groups and Democratic lawmakers, who stand to lose political power if, as many fear, undocumented immigrants and their families refuse to respond to the survey.

The suit names the Census Bureau and its acting director as well as the U.S. Department of Commerce, which oversees it, and Ross.

In announcing it, New York Attorney General Eric T. Schneiderman accused the administration of being “out to destroy” the constitutionally mandated count. He said it would depress turnout in immigrant-heavy states and mocked U.S. Attorney General Jeff Sessions for saying the question was necessary to enforce the 1965 Voting Rights Act, noting that Sessions has called the act “an intrusive piece of legislation.”

The lawsuit asserts that adding the question violates the mandate in the U.S. Constitution to conduct an “actual Enumeration” every 10 years to determine “the whole number of persons” in the United States, and it calls the survey “one of the most critical constitutional functions our federal government performs.”

Census tallies are used to determine the distribution of representation and resources, including the number of seats in the U.S. House of Representatives, the number of electoral college votes, and the apportionment of hundreds of billions of federal dollars each year. The District uses U.S. census information to draw boundaries for wards, Advisory Neighborhood Commissions, and voting precincts.

Fourteen percent of the District’s population is foreign-born, and an estimated 25,000 immigrants are undocumented. Attorney General Karl A. Racine said the citizenship question could undermine residents. “This capricious decision by the Trump administration increases the likelihood that residents in our city will decline to participate in the census out of fear,” he said. “When residents are not counted for any reason, our resources and representation suffer, and our community suffers.”

In Maryland, where nearly 15 percent of people are foreign-born and around 250,000 are undocumented, Attorney General Brian E. Frosh (D) said the question would result in the loss of federal funds for the state and deprive it of fair representation in Congress. “This maneuver will not withstand constitutional scrutiny,” he said.

Virginia Attorney General Mark R. Herring (D) called the question a “poison pill from the Trump administration [that] is about ideology, not accuracy,” and he added that “there is no question that this is just another attempt to intimidate and instill fear in immigrant communities.”

In Virginia, immigrants account for around 12 percent of the population and 300,000 are undocumented. The state received more than $953 million in Highway Trust Fund grants, more than $131 million in Urbanized Area Formula Grants, and nearly $64 million in Child Care Development grants in fiscal year 2015, all based on census data, Herring’s office said.

The United States is home to 43 million foreign-born people, including an estimated 11 million undocumented immigrants. Even those who are citizens or who reside here legally could be reluctant to fill out the household-wide survey if others in their home are undocumented, critics say.

The lawsuit charges that minority and immigrant populations are already among the hardest to count and that adding a citizenship question at this point would reduce the response rate and would depart from the standard practice of researching and testing a new question for several years before adding it. It notes that in 1980 the Census Bureau fought a lawsuit to compel it to include a question about immigration status on the decennial survey, saying it would “severely jeopardize the overall accuracy of the population count.”

Tom Cochran, executive director of the U.S. Conference of Mayors, which represents mayors of cities with 30,000 or more residents, said adding the question could hurt cities regardless of party. “Mayors of both parties have long contested that previous censuses have undercounted cities, limiting the federal resources that their communities deserve,” he said.

Schneiderman said he is ready to take the case to the Supreme Court but doubts it will need to go that far. Noting successful litigation blocking administration action against the Deferred Action for Childhood Arrivals program and the travel ban against people from certain countries, Schneiderman noted that Trump’s own comments about such issues have been used to prove animus, or ill will.

“His Twitter account is the gift that keeps on giving, as far as lawyers are concerned,” he said.

Maria Sacchetti contributed to this report.