When is an immigrant not a person? According to President Donald Trump, it’s whenever the executive branch says so. The president has spent the past four years promulgating this idea for the purposes of excluding undocumented immigrants from the numbers used to calculate each state’s representation in Congress. Even though he is on his way out of office, this notion may become enshrined into law by the Supreme Court, which will hear oral arguments on a key case, Trump v. New York, on Monday. How the Roberts court rules could substantially tilt the balance of power in the legislature and ensure that some measure of Trumpism endures long into the Biden administration.

The Constitution requires the president to count the “whole number of persons in each State” through the decennial census. Congress then uses that number to apportion each state’s seats in the House of Representatives and, by extension, its votes in the Electoral College. The Constitution’s framers considered but rejected counting “citizens” or “voters,” fearing those terms could be manipulated by state or federal governments for political advantage. Instead, they chose “persons”—a word that would seem to have no wriggle room.

Nonetheless, the Trump administration will try to get the Supreme Court to agree that undocumented immigrants are not “persons” who must be included in the count. Should the president succeed, he will alter the very basis of our representational democracy—a system that has fully counted all of the people living in the United States since the abolition of slavery put an end to treating slaves as three-fifths of a person.

From a moral standpoint, the claims to personhood among undocumented immigrants is plain: To say otherwise is to deny their very humanity. But if the court’s conservative majority truly believes in originalism, it should find ample reason to rule against the president, for the same practical reasons that motivated the Constitution’s framers to choose that term: to prevent manipulation of apportionment for the benefit of the party in power. If undocumented immigrants can be excluded, then future presidents have a strong incentive to wield the executive’s extraordinary power over immigration status for partisan political gain, defining for the nation who is a “person” to be counted and who is not.