A citizenship question on the 2020 census has already drawn challenges from states that fear an undercount of immigrants and a loss of federal funds. But demographers say there could be even deeper consequences: The question could generate the data necessary to redefine how political power is apportioned in America.

Republicans officials, red states and conservatives behind a series of recent court cases have argued that districts historically allotted based on total population unfairly favor states and big cities with more undocumented immigrants, tilting power from states like Louisiana and Montana to California and New York. Congressional seats and state legislative districts should equally represent citizens or eligible voters, they say, not everyone.

Until now, their arguments have faced a logistical challenge. The government doesn’t currently count citizens as thoroughly as it does the total population, tallying every person on every block.

“If the day comes that one of these suits succeeds in court, the 2020 count would provide the data to allow states to implement a redefinition of ‘the people,’ ” Taeku Lee, a professor of law and political science at the University of California, Berkeley, wrote in an email.