(Bloomberg) -- Commerce Secretary Wilbur Ross was accused of distorting a conversation with a Nielsen Co. executive to back the Trump administration’s view that adding a question about citizenship to the 2020 census wouldn’t cut the response rate of immigrants and noncitizens.

Christine Pierce, a senior vice president of data science at Nielsen, said in an Oct. 25 affidavit that Ross mischaracterized views she shared with him during a 20-minute phone call he requested in March. That is according to a filing Tuesday in federal court in Manhattan, where dozens of states and cities have filed a lawsuit that seeks to prevent the planned question from being added to the census.

“During this conversation, I told Secretary Ross unequivocally that I was concerned that a citizenship question would negatively impact self-response rates,” Pierce said in the affidavit. “I explained that people are less likely to respond to a survey that contains sensitive questions.”

The question, which hasn’t appeared on the once-a-decade survey since 1950, reads, “Is this person a citizen of the United States?”

Ross, whose department oversees the Census Bureau, said in documents describing his conversation with Pierce that she agreed there was no empirical evidence to suggest that such a question would damp response rates. Pierce said in her affidavit that extensive testing would be required to determine the impact of the question and that the bureau had done no such testing.

A call to the Commerce Department seeking comment on the affidavit wasn’t immediately returned.

  • More: NYC Could Lose Money, Power With Trump Citizenship Question

The plaintiffs have previously accused Ross of distorting facts. Before the trial began, he changed his claim that he decided to add the question only after the Justice Department requested it to help enforce the Voting Rights Act, after the states found contrary evidence.

The affidavit was filed by New York Attorney General Barbara Underwood, who is leading the plaintiffs in the case. They claim President Donald Trump’s administration is adding the question to scare immigrants away from participating in the census to dilute their political power. The idea is that, with the president’s rhetoric about immigrants in the air, people approached by census takers may worry the data could be used by federal immigration agents to target them or someone in their household, even if they are in the U.S. legally.

The U.S. says that claim is built on “unrelated innuendos” and that the question will improve the accuracy of the census, allowing the government to better enforce the voting rights law. The plaintiffs say Ross added the voting rights explanation as a pretext to justify a discriminatory policy change. The Census Bureau has other, already tested methods of gathering citizenship information to help the government enforce the law.

  • More: Citizenship Question Goes on Trial on Eve of Crucial Vote

The trial, which coincided with Tuesday’s momentous midterm election, could help rewrite the nation’s political map for a decade or more. Census results are used to apportion U.S. congressional seats and divvy up the Electoral College votes that determine the winners of presidential elections. The data are also used to distribute hundreds of billions of dollars a year in federal aid to states and localities.

U.S. District Judge Jesse Furman, an appointee of former president Barack Obama, is overseeing the two-week trial without a jury. The outcome could give either Democrats or Republicans an edge as soon as 2021 and through at least 2031, just after the next decennial census. Given the stakes, an appeal to the U.S. Supreme Court is all but inevitable.

More: The 2024 Presidential Election May Be Decided in a NYC Courtroom

The case is State of New York v. U.S. Department of Commerce, 18-cv-2921, U.S. District Court, Southern District of New York (Manhattan).

To contact the reporter on this story: Erik Larson in New York at elarson4@bloomberg.net

To contact the editors responsible for this story: David Glovin at dglovin@bloomberg.net, Peter Jeffrey

©2018 Bloomberg L.P.