The states argue that including this question will lead fewer Americans to be counted in the census and violate the Constitution, which calls for the national survey of both citizens and noncitizens every 10 years in order to redraw congressional districts and school boards, as well as allocate grants for things like infrastructure projects.

Previous versions of the U.S. Census included a section about citizenship, but the question was removed from the decennial census after 1950.

“The census is supposed to count everyone,” said Attorney General Maura Healey of Massachusetts. “This is a blatant and illegal attempt by the Trump administration to undermine that goal, which will result in an undercount of the population and threaten federal funding for our state and cities.”

Officials in Massachusetts, as well as Connecticut, Delaware, Illinois, New Jersey, New Mexico, Oregon, Pennsylvania, Rhode Island, and Washington will join Attorney General Eric Schneiderman of New York in a multi-state lawsuit challenging the addition of the citizenship question. On Monday night, California filed a separate lawsuit.

The addition of a citizenship question “will create an environment of fear and distrust in immigrant communities that would make impossible both an accurate census and the fair distribution of federal tax dollars,” Schniederman said.

Each year, more than 130 programs use Census data to allocate more than $675 billion in funding.

Commerce Secretary Wilbur Ross, whose department oversees the Census Bureau, said the additional question was necessary to protect voting rights. White House spokeswoman Sarah Sanders repeated this sentiment to reporters at the press briefing Tuesday, though civil rights leaders refute that claim.

Ross pointed out that questions about citizenship are included in the American Community Survey, the voluntary questionnaire also conducted by the Census Bureau that captures a much smaller sample of the population each year to help inform decisions about state and federal funding. Adding that “neither the Census Bureau nor the concerned stakeholders could document that the response rate would in fact decline materially.”

But experts say that the American Community Survey differs so substantially from the decennial census that using evidence from one to make decisions about the other without further testing is misguided. Six former directors of the Census Bureau sent a letter to Ross in January saying they were “deeply concerned” that adding the citizenship question would “considerably increase the risks” to the 2020 Census.

“When you do this once every 10 years, for 340 million people, you’ve got to get it right,” William H. Frey, a University of Michigan demographer, told the New York Times.

A test run of the 2020 Census is already underway in Providence, R.I., where the mailers do not include the citizenship question.