DENVER – Colorado has joined a lawsuit involving 18 states, several cities and counties and the U.S. Conference of Mayors aiming to block the Trump administration from putting a citizenship question on the 2020 U.S. Census.

But the state is doing so without the representation of its attorney general’s office and will have the governor’s chief legal counsel, Jacqueline Cooper Melmed, represent the state in the proceedings.

Gov. John Hickenlooper’s office signed on to the first amended complaint in the lawsuit on Monday. New York Attorney General Eric Schneiderman and a host of other states originally filed the lawsuit last month in the U.S. District Court for the Southern District of New York.

Hickenlooper, a Democrat, broke with Colorado Attorney General Cynthia Coffman, a Republican, in filing the suit.

Coffman in early April announced that she and the attorneys general for Oklahoma and Louisiana supported the new citizenship question, saying that U.S. Secretary of Commerce Wilbur Ross was “within his authority to find that the need for accurate citizenship information outweighed the fears of a lower response rate.”

But in joining the suit, the governor’s office argued otherwise.

“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.”

Annie Skinner, the spokesperson for the attorney general's office, outlined the differences in opinion between Hickenlooper and Coffman and explained the process by which Colorado joined the lawsuit:

"The Attorney General has already expressed her views on the topic, and she stands by her opinion that the citizenship question should be included on the 2020 Census. She believes it is critically important to ensure the Census creates as accurate a picture as possible of the makeup of our diverse country so that all people that live within the United States can be appropriately represented. The Governor has a differing opinion on the matter, and Colorado law provides for the Governor to have counsel appointed to him in these circumstances, and for that counsel to be designated as a Special Assistant Attorney General. The appropriate steps have been taken to ensure the Governor has counsel."

Hickenlooper signed a letter sent to Ross in February by some of the states that eventually sued over the question urging him not to add the question.

The suit notes that nearly 21 percent of Colorado households didn’t mail back their 2010 questionnaire and had to be followed-up with and says that number could be similar or worse if there is a citizenship question added.

The suit says there were about 200,000 undocumented immigrants in Colorado as of 2014, and that more than 275,000 Colorado residents – half of whom were born in the U.S. – lived with one or more undocumented family member between 2010 and 2014.

The suit says that billions of dollars in federal money used for transportation, education and health care, among other things, is at risk if Colorado’s population isn’t accurately counted.

It also notes that the Commerce Secretary and Justice Department’s recommendations to include a citizenship question goes in the face of recommendations from the Census Bureau.

Colorado and the other plaintiffs argue that the citizenship question violates the Enumeration Clause of the Constitution, which requires an accurate count. It was also brought under the Administrative Procedure Act, so that if the court finds in the plaintiffs’ favor, they could toss the order by saying it was arbitrary or capricious.

The U.S. Census has not officially asked a citizenship question since 1950, though it has continued to appear in the American Community Survey. And some of the long-form questionnaires sent to some citizens each decade since then did include a question, though the question was not included on the full survey.

The Census Bureau has used the American Community Survey for local household data since 2005. The Bureau has a guidance form detailing which questions it plans to ask on the 2020 Census and why.

At least 17 states and six studies have sued over the 2020 question, and the limited testing that has been done so far, which has had questionable results, did not include the question, according to The Associated Press.

Coffman voiced her support of the citizenship question while she was still a Republican candidate for governor. But she failed to get enough support at the state assembly in April to make the June primary ballot – ending her quest for the governorship.