With House Republicans looking down the barrel of an electoral wipeout in the upcoming midterms, the Trump administration has asked the Commerce Department to develop the political equivalent of a weapon of mass destruction: a rule change that could have sweeping implications for the division of power in the United States, and could fortify G.O.P. gains for a decade. On the surface, the request sounds picayune. As the Commerce Department explained in a statement Monday, “a question on citizenship status will be reinstated to the 2020 decennial census questionnaire to help enforce the Voting Rights Act”—the same question, the department notes, “that is asked on the yearly American Community Survey.” Inquiries about citizenship were standard from 1820 through 1950, when the topic was dropped from the decennial questionnaire.

Critics, however, see a wolf in sheep’s clothing. The Census, after all, is more than just a statistical survey on the U.S. population—it also serves to determine the allocation of public funds and, most important, congressional and state districting. Democrats fear that a question about citizenship status will discourage millions of undocumented immigrants from participating, significantly skewing the results and disempowering cities and communities that tend to lean left. “The census numbers provide the backbone for planning how our communities can grow and thrive in the coming decade,” said Xavier Becerra, California’s attorney general, who immediately said he would challenge the decision. “What the Trump administration is requesting is not just alarming; it is an unconstitutional attempt to discourage an accurate census count.” On a more prosaic level, the census question could distort all sorts of civil planning and infrastructure projects that require an accurate accounting of the number of people using them. “Adding this question will result in a bad census—deeply flawed population data that will skew public and private sector decisions to ensure equal representation, allocate government resources, and anticipate economic growth opportunities—for the next 10 years,” Vanita Gupta, the chief executive of the Leadership Conference on Civil and Human Rights, told The New York Times.

The Census change springs from a somewhat obscure legal debate among some Republicans, who have quietly examined ways to manipulate the decennial survey to effectively gerrymander districts. Federal law requires that congressional districts be drawn based on the total population—a number including non-citizens and children. But in 2016, the Supreme Court ruled that this “one person, one vote” standard did not need to be applied to states when they draw boundaries for local legislative districts. (Further details were left to be worked out in future cases.) The ruling provided Republicans with a template to solidify their already sizable gains at the state and local level throughout the country. Since 1950, the Census hasn’t included the necessary data for Republicans to make that “one citizen, one vote” vision a reality. An updated Census, however, with both information on citizenship status and suppressed responses from households that include undocumented immigrants, could permanently tip the scales. More Republicans in control of more statehouses, in other words, would ultimately mean more congressional districts drawn in their favor.

The weaponization of the Census underscores how even the most technical, bureaucratic processes underlying democratic governance have become twisted by partisan warfare. Beyond the matter of Democratic or Republican control of state legislatures, and the congressional districts they draw, are life-and-death questions for a 21st-century, data-driven nation: how many people live where, and in what circumstances; the age and distribution of populations that are vulnerable to potential epidemics; the economic effects of pollution and climate change; how resources should be allocated to combat poverty and reduce crime. “The Census Bureau operates carefully when it comes to changing the decennial census or any of the numerous surveys,” University of Florida politics professor Michael McDonald tweeted on Tuesday. “They field test changes to estimate effects. Sec. Ross made a decision without any such testing.”