President Trump departs a July 2019 press conference on the census with U.S. Attorney General William Barr (center) and Commerce Secretary Wilbur Ross in the White House Rose Garden.

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President Trump departs a July 2019 press conference on the census with U.S. Attorney General William Barr (center) and Commerce Secretary Wilbur Ross in the White House Rose Garden.

Alex Wong/Getty Images

President Trump is signing a memorandum Tuesday that calls for an unprecedented change to the constitutionally mandated count of every person living in the country — the exclusion of unauthorized immigrants from the numbers used to divide up seats in Congress among the states.

The White House has not provided any additional details and has not yet released the text of the memorandum, but in a written statement, a White House official who spoke on background said the “action will clarify that illegal aliens are not to be included for the purpose of apportionment of Representatives following the 2020 Census.”

But the move by the president, who does not have final authority over the census, is more likely to spur legal challenges and political spectacle in the last months before this year’s presidential election than a transformation of the once-a-decade head count.

Since the first U.S. census in 1790, both U.S. citizens and noncitizens — regardless of immigration status — have been included in the country’s official population counts.

The fifth sentence of the Constitution specifies that “persons” residing in the states should be counted every 10 years in order to determine each state’s share of seats in the House of Representatives. The 14th Amendment goes further to require the counting of the “whole number of persons in each state.”

It is Congress — not the president — that Article 1, Section 2 of the country’s founding document empowers to carry out the “actual enumeration” of the country’s population in “such manner as they shall by law direct.”

In Title 2 of the U.S. Code, Congress detailed its instructions for the president to report to lawmakers the tally of the “whole number of persons” living in each state for the reapportionment of House seats. In Title 13, Congress established additional key dates for the “tabulation of total population.”

The state of Alabama, however, is arguing in an ongoing federal lawsuit that the framers of the Constitution did not intend for the term “persons” to include immigrants living in the country without authorization. Alabama says it’s trying to avoid losing a seat in Congress after the 2020 census by seeking to leave out unauthorized immigrants from the results of the national count that are used to reapportion the U.S. House.

Trump’s announcement, first signaled in a Politico newsletter last week, comes just over a year after the administration backed down in its failed attempt to add the now-blocked citizenship question to the 2020 census.

Last July, the president issued an executive order to use government records, including from state DMVs and federal agencies such as the Department of Homeland Security, to produce anonymized citizenship data that could be used to redraw voting districts in a way that, a GOP strategist concluded, would politically benefit Republicans and non-Hispanic white people.

With the national census self-response rate at just over 62%, the White House announcement threatens to derail the Census Bureau’s efforts to finish tallying up roughly four out of ten households that have not filled out a census form on their own.

The agency’s operational plan for the 2020 census includes specially designed efforts, such as providing online forms and call centers in 13 languages, to try to make sure the census includes undocumented immigrants and other populations the bureau considers “hard-to-count.”

According to the Census Bureau’s residence criteria for determining how to count different groups of residents for the 2020 census, citizens of foreign countries who are living in the U.S. are supposed to be counted “at the U.S. residence where they live and sleep most of the time,” while international visitors should not be counted.

The bureau has been relying on ads and community groups in order to help ramp up its outreach to households with immigrants, people of color and other historically undercounted groups, many of whom remain distrustful of sharing their information with the government despite federal laws that require the Census Bureau to keep personally identifiable census information confidential until 72 years after it’s collected and prohibit that information from being used against an individual.

The administration has also raised concerns in recent weeks by making two new political appointments at the bureau. The move has sparked an inquiry by the inspector general for the Commerce Department, which oversees the bureau. Democratic lawmakers and professional associations, including the American Statistical Association and the American Economic Association, are questioning whether the appointments of Nathaniel Cogley, a political science professor, and Adam Korzeniewski, a former political consultant to a YouTube personality known for racist pranks, are a partisan attempt to interfere with the census.

NPR White House correspondent Tamara Keith contributed to this report.