Why can’t the U.S. Census ask a very simple question?

Should the 2020 U.S. Census ask about citizenship? Commerce Secretary Wilbur Ross decided that it should, and his decision triggered an explosion of legal challenges.

Last week, a federal judge in New York ruled that the question may not be asked. U.S. District Judge Jesse Furman wrote, “Secretary Ross’s decision to add a citizenship question to the 2020 census—even if it did not violate the Constitution itself—was unlawful for a multitude of independent reasons and must be set aside.”

Furman said Ross ignored the Census Bureau’s research showing that asking about citizenship would likely result in an undercount.

The U.S. Constitution requires the government to conduct a census every 10 years to count the population and apportion seats in Congress accordingly. The information gathered by the nationwide headcount is also used to allocate federal funds for programs including the Supplemental Nutrition Assistance Program and Section 8 housing vouchers. And the population numbers are used to draw election districts.

Furman said asking the citizenship question would result in a “significant reduction” in response rates from noncitizen and Hispanic households. “That undercount will, in turn, result in a loss of political power and funds, among other harms, for various plaintiffs,” he wrote.

Furman’s decision is likely to be appealed, but in the meantime, another lawsuit over the citizenship question went to trial in a federal court in Maryland this week. MALDEF, the Mexican American Legal Defense and Educational Fund, has joined with a group called Asian Americans Advancing Justice along with a long list of other plaintiffs to challenge the citizenship inquiry.

MALDEF says its lawsuit is the first and only to include a claim that officials of the Trump administration conspired with others “to deprive immigrants of color of their constitutional rights to equal representation and to fair allocation of federal funds.”

The lawsuit names Trump and Ross as co-conspirators along with former White House advisor Steve Bannon and Kris Kobach, then the Kansas secretary of state. The plaintiffs said in a press release that they will present evidence that the citizenship question is the product of a conspiracy “to violate the civil rights of communities of color.”

There are about half a dozen lawsuits challenging the citizenship question, and now Congress is getting involved, too.

The House Oversight Committee has called on the commerce secretary to answer questions about his efforts to have the census ask about citizenship. This week, the committee released a statement saying Ross will testify at a hearing on March 14, and the committee “expects full compliance with all of our outstanding document requests prior to the hearing.”

It seems certain that all the legal wrangling will succeed in delaying a decision beyond the deadline for the 2020 Census to be finalized, even if the U.S. Supreme Court eventually rules in favor of the administration. The next census is in 2030, when a different president will be in the Oval Office.

The Trump administration has said it needs the citizenship question on the Census in order to fulfill its obligations to enforce the Voting Rights Act of 1965, a federal law intended to protect minorities from discrimination.

Voting might be at the heart of the issue.

In terms of representation and federal programs, the only difference between a citizen and a permanent legal resident is the right to vote. A citizen has it. A permanent legal resident does not.

If the Census collects hard data on how many citizens of voting age reside in any given district, city, county or state, it would enable a comparison between census data and voter rolls, possibly turning up evidence that non-citizens are voting. For instance, if the Census Bureau says there are 25,000 citizens of voting age in a jurisdiction, it would be news if 30,000 ballots were cast in an election there.

And then there’s the elephant in the room.

No one really knows how many undocumented immigrants reside in the United States, but the alarm voiced by the plaintiffs in the lawsuits challenging the citizenship question suggests that the number is far higher than the 11 million figure commonly cited.

The future of immigration policy could be dramatically affected by hard data showing the number of households that refuse to respond to a Census that asks about citizenship.

It can be risky to ask a question if you don’t already know the answer, even more so if you do.