Commerce Secretary Wilbur Ross in Washington on July 16. (Manuel Balce Ceneta/AP)

THE CENSUS has a clear purpose: to count how many people live in the United States and determine the population’s general characteristics. The Constitution mandates a census every 10 years, and some of the nation’s most important decisions are based on its data — such as the allocation of congressional seats and electoral college votes. Because of its reputation for quality and care, businesses rely on census data to make their own crucial investment decisions.

The Trump administration seems to be doing everything it can to bias the 2020 count.

To vouchsafe an accurate tally, Congress has twice enshrined in law the principle that all individual census forms must be confidential. Each response becomes one nameless entry into a vast pool, anonymized in the aggregated data the Commerce Department eventually releases. Federal lawmakers have prescribed massive penalties for Commerce Department officials who share secret census information with other branches of the government. If people knew their responses might be shared with the FBI or immigration authorities, many would lie on their forms — or decline to fill them out at all.

The Trump administration is muddying this picture and fiddling with that clear principle. First, it added a question on people’s citizenship status to census forms. The census’s own experts objected that adding the question would discourage participation among immigrants, and they said the government can get more reliable citizenship data in other ways.

Then, in defending a lawsuit over the citizenship question, the Justice Department turned over documents suggesting that its officials have considered the possibility of census data being shared with law enforcement. That would be lawless. But even raising the possibility will fan fears that President Trump’s federal government cannot be trusted to keep individual responses confidential.

Which may be exactly the point. If undocumented or documented immigrants — or even naturalized U.S. citizens who understandably fear what this administration might do to them — refuse to cooperate with the census, then areas with many immigrants will seem less populated than they are. Those areas tend to be in places that vote for Democrats. Depressing the count in blue areas means they get less federal money and less congressional representation.

In another time, this theory might seem paranoid. But after the GOP’s multifaceted and continuing campaign to discourage voting among poor and minority citizens, it seems perfectly in character.