The Justice Department said in December it wanted the citizenship question included to help enforce Section 2 of the Voting Rights Act, aimed at voting rights violations. "I find that the need for accurate citizenship data and the limited burden that the reinstatement of the citizenship question would impose outweigh fears about a potentially lower response rate," Commerce Secretary Wilbur Ross said in an eight-page memo.
California Attorney General Xavier Becerra (D) disagreed, and he immediately announced plans to sue the Trump administration. "The census numbers provide the backbone for planning how our communities can grow and thrive in the coming decade," Becerra argued. "What the Trump administration is requesting is not just alarming, it is an unconstitutional attempt to discourage an accurate census count."
Especially in a political climate where President Trump has stoked anti-immigrant sentiment, asking respondents to tell a federal agency their citizenship status is expected to decrease the number of immigrants — both undocumented and legal residents — willing to participate in the census. That would presumably undercount the population of the urban (and Democratic) areas where immigrants tend to live, skewing congressional maps toward Republican-leaning areas. But it could also allow GOP-led states to disregard non-citizen residents in drawing state districts, helping Republicans win or retain the power to draw gerrymandered federal congressional maps. You can find more details about that concern at The Washington Post. Peter Weber