Minnesota is suing the federal government over a single question on the 2020 census — a question it argues could skew its population count and cost it everything from a seat in Congress to its share of federal funding.

The state, along with 16 other states, six cities, and the District of Columbia filed suit in federal court Tuesday, arguing that the U.S. Commerce Department's plan to ask about respondents' citizenship status is unconstitutional and could drive down response rates.

Minnesota Attorney General Lori Swanson argued in the lawsuit that any change that drives down the response rate could cost Minnesota dearly.

"The United States Constitution requires that a census be undertaken every 10 years to count every person in the United States," Swanson said in a statement. "Census Bureau directors appointed by presidents of both political parties have not included a question about citizenship since 1950 — nearly seven decades ago — out of concern that it would result in an inaccurate count."

Commerce Secretary Wilbur Ross, whose agency oversees the decennial census, announced the return of the citizenship question last week — bypassing the years of painstaking deliberation and review that usually precedes any change to the questionnaire. The change came at the request of the U.S. Department of Justice, which argued that it needed an accurate count of noncitizens to root out any potential violations of the Voting Rights Act.

Ross argued that the optional long-form census has included a question about citizenship every year except 2010 and that there is no "empirical evidence" that including a citizenship question on the mandatory short-form census would drive down response rates.

Doug Wardlow, a Republican running against Swanson for attorney general, accused her of "pointlessly ginning up fear" among immigrants with the lawsuit.

"Swanson and the other Democrats have two objectives, both of which are political," Wardlow said in a statement. "They are worried that illegal immigrants won't answer the census questionnaire if it has a question about citizenship. They want to make sure that sanctuary cities don't see their representation or federal dollars threatened."

Fear of targeting

The Constitution requires an accurate count of all the people — not just the citizens — living in American cities, counties and states.

Before the government can distribute Highway Trust Fund grants to each state, it needs to know how many people are driving on the roads — the 2010 census set Minnesota's share at $673 million. Before it can distribute Child Care Development grants — $63 million worth, in Minnesota's case — it needs an accurate count of the state's children.

But convincing immigrants and minority groups to fill out a census form has never been easy. The new citizenship question, some worry, will reinforce the perception that the Trump administration is targeting immigrants and refugees.

"We have a lot to lose if every Minnesotan is not counted," said John Keller, executive director of the Immigrant Law Center in Minnesota.

"This is going to be one of the most challenging censuses," added Keller, whose agency was often asked to encourage immigrant communities to fill out and return census forms. "Even if there wasn't a citizenship question introduced into the census, we would have been looking into, I think, historic undercounting."

Even second- or third-generation citizens, Keller said, might be reluctant to respond to a government document or a census taker's knock on the door if they fear it could jeopardize members of their extended families.

The lawsuit said adding the citizenship demand to the 2020 census questionnaire was an arbitrary decision that will "fatally undermine the accuracy of the population count." The NAACP has also argued that the plans for the census will lead to a massive undercounting of blacks.

The lawsuit noted that in 2010, 14 percent of Minnesota households did not mail back their 2010 census questionnaire, requiring an in-person follow-up. Immigrants made up a little more than 8 percent of Minnesota's population and as of 2014, nearly a quarter of them were undocumented.

Could affect House seat

The 2020 census results will set Minnesota's federal funding formulas and could determine whether the state loses of one of its eight House seats — a real possibility, even with an accurate head count.

State demographer Susan Brower said changes to the census questionnaire usually come after years of painstaking research and testing to ensure the question, or even the wording of the question, will not affect response rates.

"It's really hard to overstate how important census data are," she said Tuesday, noting that the same numbers that determine how much federal money flows to states then decides how much state assistance will filter down to individual communities for things such as schools, roads and local government aid.

"We know that the data we'll be using [for congressional reapportionment and other purposes] will be of poorer quality, because we will have missed people," said Brower, echoing concerns that the citizenship question could drive down response rates among noncitizens and citizens alike and increase fears that government agencies cannot be trusted.

"That's the opposite of what we should be doing if we want to get a good count," she said.