WASHINGTON — The Trump administration is adding a question about citizenship to the 2020 Census, and that is bad news for Illinois, no matter your politics.

Illinois now has 18 House seats in Congress. Population declines already charted mean Illinois is on course to lose one or two seats, according to an analysis by the respected Election Data Services company.

The inclusion of the intimidating citizenship question puts President Donald Trump’s thumb on the scale — and makes a drop to 16 Illinois seats more likely after the 2020 Census.

If self-serving politics were always logical, all 18 Illinois House incumbents — 11 Democrats and 7 Republicans — would show the same concern about getting the most accurate count possible for Illinois. Only Democrats are sounding the alarm.

Why a possible undercount?

Non-citizen immigrants — who cluster in urban, i.e. Democratic cities — may well be afraid in this Trump era to respond to the census. That could create significant undercounts in states like Illinois with major immigrant populations.

Trump has been targeting immigrants since he started running for president. The wall. Travel bans. Yanking “Dreamer” protections. Going after sanctuary cities, of which Chicago is one.

People have to trust that the information provided to the census will not be used against them.

During a phone briefing for reporters on Tuesday, Arturo Vargas, the executive director of NALEO — the National Association of Latino Elected and Appointed Officials Education Fund — said the Trump administration’s use of the question was a “scare tactic” to prevent Latinos and others from “participating” in the 2020 census.

The Commerce Department announced the addition of the question on Monday night.

Quick refresher!

The Constitution requires a census every 10 years. The census is used to reapportion the House of Representatives.

Reapportionment determines the allocation of the 435 congressional seats. States gaining population in a census get more seats. States with a population decline lose seats.

The census is also used to determine to a large degree the flow of federal funds to states. Many federal programs are based on a per-person formula. The more people, the more money.

So Republican Gov. Bruce Rauner should be for the most accurate count, right? Illinois is marching toward bankruptcy. We can use the money. I asked his government and political spokespeople for his reaction, and so far they don’t have one.

Democratic nominee J.B. Pritzker taunted Rauner on this in a tweet. “This is a direct attack on immigrant communities by the Trump administration, and it can only worsen the response rate of immigrant residents in Illinois. When will @BruceRauner stand up for Illinois’ families and fight this latest attack?”

The politics?

Most of the big immigration states are Democratic. The attorney generals in California and New York are suing the Trump Administration over this. Illinois Attorney General Lisa Madigan is joining the New York lawsuit.

What does the Constitution say?

Non-citizens count.

Section 2 of the Fourteenth Amendment states that “Representatives shall be apportioned among the several States according to their respective numbers, counting the whole number of persons in each State, excluding Indians not taxed.”

As The Brennan Center for Justice at the New York University School of Law notes in an essay, “The Constitution uses the word “numbers” or “persons” — not “citizens” or “legal residents” or “those lawfully present.”

Census questions are subject to testing. Was the citizenship question tested?

No.

The single pre-census test takes place on April 1, 2018, in Providence County, Rhode Island. This question is coming so late it is not part of the test.

Commerce Secretary Wilbur Ross said in a statement the question needed to be asked for “more effective enforcement” of the Voting Rights Act. Civil rights lawyers say that’s baloney.

Ross said he determined — with no testing — the “legitimate government purpose outweighed the limited potential adverse impacts.”

A group of Democratic senators, including Sen. Tammy Duckworth, D-Ill., are sponsoring long-shot legislation to “prohibit last-minute changes or additions to the census without proper research, studying, and testing.”

As Rep. Jan Schakowsky, D-Ill., said in a tweet, “This nativist, and quite possibly illegal, move will completely compromise the census and is designed to undercount and underfund immigrant communities.”