Top law enforcement officials in 19 states urged the Commerce Department on Monday to reject a request from the Trump administration to add a citizenship question to the 2020 Census, which they said would be unconstitutional.

“Adding a citizenship question — especially at such a late date in the 2020 Census planning process — would significantly depress participation, causing a population undercount that would disproportionately harm states and cities with large immigrant communities,” the attorneys general wrote. “This undercount would frustrate the Census Bureau’s obligation under the Constitution to determine ‘the whole number of persons in each state,’ threaten our states’ fair representation in Congress, dilute our states’ role in the Electoral College, and deprive our states of their fair share of hundreds of billions of dollars in federal funds that are allocated in part on decennial Census data.”