Within hours of the Commerce Department’s announcement last Monday that there will be a question about citizenship on the 2020 Census, the state of California had gone to court to block it. Announcing the lawsuit, California Attorney General Xavier Becerra claimed that the Constitution bars the Census Bureau from asking people who live in America if they are U.S. citizens. That sounds ridiculous, because it is.

“The Constitution requires the actual enumeration of all people in every state every 10 years,” Becerra said. “By including a citizenship question which will diminish response rates, the census will not be able to fulfill its constitutional duty to count everyone.”

California’s claim (echoed by 12 other states that filed a separate suit the next day) is that if the census questionnaire asks about citizenship status, some undocumented immigrants will be too spooked to answer. That may be true; it may be a good reason to refrain from asking the question. But it doesn’t remotely follow that asking it is unconstitutional.

The census has been posing questions about citizenship, off and on, for 200 years. The 1820 Census asked whether individuals were “foreigners not naturalized” — that is, noncitizens — and the question was repeated in 1830 and 1840. Respondents were queried more explicitly about citizenship status in 1870, and the question returned in every census from 1890 through 1950.

In short, the census has been enumerating citizens for nearly as long as it has been enumerating residents. To inveigh against the practice now as a violation of the Constitution — as, in former attorney general Eric Holder’s description, “a direct attack on our representative democracy” — is overwrought hyperbole, red meat for the progressive base, not a serious legal argument.

All the same, that doesn’t mean that putting a citizenship query on the 2020 Census is a sensible idea. A policy decision can be misguided, as this one is, without being unlawful.

The administration maintains that citizenship data is needed for proper enforcement of the Voting Rights Act, which relies on estimates of the number of voters in each state and district. But that’s disingenuous. Since 2000, the Justice Department has enforced the act with citizenship data extrapolated from the American Community Survey, a questionnaire sent each year to about 2.6 percent of the population. There isn’t any compelling reason to revert to a citizenship question in the decennial census.

Is the administration trying deliberately to depress the response rate from undocumented immigrants? Maybe not. Then again, some Republicans, like Sen. David Vitter of Louisiana, have openly fumed that if the census doesn’t focus on citizenship, “states that have large populations of illegals would be rewarded.” Such cynicism may be inseparable from politics. But there’s no reason why it must be allowed to degrade the census.

Unfortunately, that degradation has spread well beyond immigration politics.

The Constitution requires only that “the whole number of persons in each State” be counted every decade for purposes of congressional apportionment. It says nothing about using the census to dredge up vast amounts of demographic and economic data. No one objects to accurate data, but everyone should object to using the intimidating power of the federal government to extract that data under threat of punishment.

If Becerra and the other AGs are genuinely concerned about keeping the census within proper bounds, they should be pressing to exclude more than the question about citizenship. The census questionnaire shouldn’t ask whether respondents are of Hispanic origin. It shouldn’t ask people to assign themselves to a racial category. It shouldn’t ask whether they own or rent their homes. It shouldn’t ask if they have a mortgage.

In the 21st century, there is no lack of sophisticated tools for amassing data, both comprehensive and granular, about the American population. That’s not the function of the federal census. Just as the Census Bureau doesn’t delve into politics, religion, or sexual orientation, it shouldn’t delve into any characteristic that goes beyond a basic population count. Who lives here, and how old are they? That’s all the Constitution requires, and it’s enough.

Jeff Jacoby is a columnist for The Boston Globe.