Colorado is suing the Trump administration to keep census takers in 2020 from asking about citizenship.

Gov. John Hickenlooper said Tuesday afternoon that Colorado will join the lawsuit by a coalition of 18 states and Washington, D.C., as well as nine cities, four counties and the U.S. Conference of Mayors.

“We have a responsibility to Colorado to see that every person is counted,” Hickenlooper said in a statement. “Our action seeks to ensure the census is being used for its intended purpose under the Constitution. An accurate census count protects federal funding and our representation in Congress.”

Colorado is joining the suit despite the fact that its attorney general, Republican Cynthia Coffman, came out in support of asking the citizenship question on April 10.

“The goal of the census is to produce as accurate a picture as possible of the makeup of our vast and diverse country so that all people that live within our borders can be appropriately represented,” she said then, days before she was eliminated from the governor’s race at the state GOP assembly. “Colorado’s next redistricting and reapportionment will be based on its 2020 Census data. We need the most complete information possible to assure fair political representation of the entire state. In fact, it is so important to be able to obtain this information that federal law provides strong privacy protections for the information that is collected, which should help overcome any reluctance to participate.”

Coffman’s office has designated Jacki Cooper Melmed, the governor’s chief legal counsel, as a special assistant AG to handle the case, said Jacque Montgomery, Hickenlooper’s spokeswoman. The amended lawsuit notes the substitution.

In March, U.S. Commerce Secretary Wilbur Ross ordered the Census Bureau to ask ever resident about his or her citizenship status. Ross and the Census Bureau are named as plaintiffs in the suit.

Plaintiffs argue that the Trump’s crackdown on immigration will scare undocumented residents from participating in the official count, for fear of attracting attention from federal authorities.

The city of Denver already has said it won’t participate in enforcing federal immigration laws. Critics call Denver, Boulder and Aurora “sanctuary cities,” spurring efforts to withhold federal grants and other repercussions on the state and federal level.

The census lawsuit was originally filed on April 3 bin the U.S. District Court for the Southern District of New York. The lawsuit can be ready by clicking here.

Besides Colorado, the other states in the complaint are Connecticut, Delaware, Illinois, Iowa, Maryland, Massachusetts, Minnesota, New Jersey, New Mexico, New York, North Carolina, Oregon, Pennsylvania, Rhode Island, Virginia, Vermont and Washington.

The cities that originally joined the lawsuits are New York, Chicago, Philadelphia, Providence, San Francisco and Seattle; and the bipartisan U.S. Conference of Mayors.

Others joining the case Tuesday were Central Falls, Rhode Island; Columbus, Ohio; Pittsburgh; Cameron and El Paso counties in Texas; and Monterey County in California.

States and cities with large immigrant populations could pay an unfair price because of a miscount in the census, as well as lose representation in the Electoral College if undocumented residents and family members who are citizens are frightened away from being counted, say critics of the Trump proposal.

The Colorado governor’s office said Tuesday that 20.9 percent of households in the state did not mail back their 2010 Census questionnaire, which required census-takers to make a personal visit. Also, Hickenlooper’s office also said immigrants make up 9.8 percent of the state’s population.

The count affects federal tax dollars for transportation, education, Medicaid and child care programs, which would have an impact on all Coloradans who use those services.

The state also notes that the Census Bureau has resisted adding a citizenship question since 1990, noting:

“Any effort to ascertain citizenship will inevitably jeopardize the overall accuracy of the population count. Obtaining the cooperation of a suspicious and fearful population would be impossible if the group being counted perceived any possibility of the information being used against them. Questions as to citizenship are particularly sensitive in minority communities and would inevitably trigger hostility, resentment, and refusal to cooperate.”