Seventeen states, the District of Columbia and six cities sued the U.S. government Tuesday, saying the addition of a citizenship question to the census form is unconstitutional.
The Trump administration's decision to ask people about their citizenship has set off worries among Democrats that immigrants will dodge the survey altogether, diluting political representation for states that tend to vote Democratic and robbing many communities of federal dollars.
Supporters of the plan for the 2020 census argue that enforcing voting rights requires more data on the voting-age population of citizens than current surveys are providing. It would be the first time in 70 years that the government uses the census form sent to every household to ask people to specify whether they are U.S. citizens.
New York Attorney General Eric Schneiderman, a Democrat who announced the new lawsuit in Manhattan federal court, said the plans would have a "devastating effect on New York, where we have millions of immigrants."
"It's unlawful. It's unfair," Schneiderman said at a news conference. He added that it would end a longstanding bipartisan effort to have the Bureau of the Census conduct a full and fair count of the population, including citizens and non-citizens.
The Census Bureau hasn't included a citizenship question in its survey of all U.S. households since 1950, well before passage of a 1965 law meant to ensure minority groups are fully represented in the once-a-decade count.
The lawsuit, which also included the bipartisan U.S. Conference of Mayors as a plaintiff, said adding the citizenship question was arbitrary and will "fatally undermine the accuracy of the population count." It asked for a ruling that the citizenship demand is unauthorized and unconstitutional.
According to the lawsuit, nearly a quarter of households in New York state did not return their 2010 census questionnaire, requiring an in-person follow-up. It noted that one-in-five New York residents were born in another country. The NAACP has also said the new plan will also lead to a massive undercounting of blacks.
A government spokesman did not immediately comment. The Justice Department has said it "looks forward to defending the reinstatement of the citizenship question." The Commerce Department has said the benefits of obtaining citizenship information "outweighed the limited potential adverse impacts."
The decennial census is required by the Constitution and used to determine the number of seats each state has in the House, as well as how federal money is distributed to local communities. Communities and businesses depend on it in deciding where to build schools, hospitals, grocery stores and more.
Several states that have slowing population growth or high numbers of immigrants such as California, New York, Illinois, Massachusetts and Ohio are typically at risk of losing U.S. House seats when their congressional districts are redrawn every 10 years — depending on how fully their residents are counted.
The defendants in the lawsuit are the U.S. Department of Commerce, responsible for the census, and the Bureau of the Census. Plaintiffs include New York, Connecticut, Delaware, Illinois, Iowa, Maryland, Massachusetts, Minnesota, New Jersey, New Mexico, North Carolina, Oregon, Pennsylvania, Rhode Island, Virginia, Vermont, Washington, the District of Columbia, New York City, Chicago, Philadelphia, Rhode Island, San Francisco, Seattle and Providence, Rhode Island.
California's attorney general filed a separate lawsuit last week that seeks to block the citizenship question from being added to the census questionnaire.
CORRECTION (April 3, 2018, 2:35 p.m. ET): An earlier version of this story incorrectly stated that several states have joined a separate lawsuit filed by California. They have not.