As in prior decades, the Census counts will include everyone for purposes of apportionment. Litigation over the issue hit procedural hurdles as it was unclear whether the data would be ready in time for President Trump to make the determination he’d flagged ultimately, the data were delayed long enough for the Biden Administration to reverse course.
On July 21, 2020, President Trump purported to suggest that he had the authority to exclude undocumented individuals from the census count - if valid, that would have affected not only how many districts the states got, but how those districts were divided within a state. After the Civil War, we amended the Constitution to ensure that each and every individual present in the country would be represented in federal districts. These population counts are calculated based on the total number of people in each state, including children, noncitizens, and others not eligible to vote. In 2012, for example, the Supreme Court approved a congressional plan in West Virginia with 0.79% population variation based on keeping county lines intact. But consistent policies that leave a relatively small spread from largest to smallest district will likely be constitutional. States must make a good-faith effort to draw districts with the same number of people in each district within the state, and any district with more or fewer people than the average must be justified by a consistent state policy.
The standard for congressional districts allows relatively small deviations, when deployed in the service of legitimate objectives.
Constitution requires that each district have about the same population: each federal district within a state must have about the same number of people, each state district within a state must have about the same number of people, and each local district within its jurisdiction must have about the same number of people.