Joshua A. Douglas is a law professor at the University of Kentucky College of Law who specializes in election law, voting rights, and constitutional law. He is the author of Vote for US: How to Take Back Our Elections and Change the Future of Voting . Find him at www.joshuaadouglas.com and follow him on Twitter @JoshuaADouglas . The opinions expressed in this commentary are his own; view more opinion at CNN. The piece has been updated to reflect the latest news.

That's not a typo: A case decided this year could impact significantly who wins the presidency five years from now.

After the Supreme Court heard oral arguments on Tuesday, it appeared that the more conservative justices may vote in favor of adding a citizenship question to the census , while the more liberal justices expressed concern about the ramifications of asking everyone whether they are citizens.

The case involves the all-important citizenship question that the Trump administration wants to include in the 2020 census: "Is this person a citizen of the United States." Seemingly innocuous on its face, the question could alter both congressional apportionment and the presidential election.

If minority communities fail to answer the census, then areas of high minority populations, such as Latino communities, will likely suffer an undercount. That would reduce their political representation.

Under the US Constitution , the federal government must count every person in the country every 10 years as part of the census. The results affect the number of congressional representatives each state receives, dictate the provision of federal tax dollars to the states and cities, and have a slew of other consequences.

Perhaps most significantly, the census results have a major impact on our elections.

The US House of Representatives has 435 seats. By taking the total population of the country and dividing by 435, the census numbers provide the average size of each congressional district. In 2010, that number was 710,767 residents per district. (The District of Columbia, with a population of around 700,000, still receives zero members of Congress, though it does have three votes in the Electoral College.) The number of congressional representatives that states receive is based on their respective state populations, using the average district size as the guidepost.

States may gain or lose congressional seats based on population shifts in the country over the preceding decade. After the 2010 census , for instance, Texas gained four seats and Florida gained two seats; New York and Ohio each lost two.

These changes alter the Electoral College as well: The number of electors in each state is equal to the number of congressional representatives plus two (the number of US Senators per state). Thus, after the 2010 census, Texas and Florida increased their Electoral College votes while New York and Ohio's electoral votes went down.

Once states know how many people reside in the state, they then must undertake the process of redistricting, where they redraw their congressional (and state) lines to comply with the principle of one person, one vote: Each district must have roughly the same number of people. Local governments must also redraw their local lines, such as for city council. The census numbers are provided down to the block level so that states know exactly how many people live in specific areas, helping them to comply with the one person, one vote requirement for each district.

Importantly, the US Constitution provides that representatives are to be awarded to the states by "counting the whole number of persons in each State." Thus, the Constitution requires congressional apportionment based on total population, not the number of US citizens. We count everyone who resides in the country, regardless of their citizenship status, and apportion the representatives accordingly.

This makes sense, because a member of Congress represents everyone in their district even if a person is ineligible to vote. No one would suggest that a person under 18 is not represented just because they can't yet vote; the same goes for someone who has not gained their citizenship.

As the briefing in the Supreme Court notes, a governmental memo suggested that the citizenship question would result in an undercount of around 6.5 million individuals. The census will reveal fewer people living in certain areas than the reality, all because the government seeks more information than is necessary in an effort to scare them into not participating.

The Electoral College already favors rural states ; a citizenship question that undercounts states with heavy concentrations of noncitizens in urban areas would dilute the influence of more populous states even further. The citizenship question could therefore change the Electoral College math in 2024, the next presidential election after the census is complete.

Of course, there's a political motivation to all of this: urban areas tend to vote for Democrats, and the citizenship question has the potential to reduce the number of representatives and federal dollars in cities with heavy Latino populations. Thus, the real goal is to change the political map.

This all comes before the process of redistricting even starts in 2021, which itself is fraught with political gamesmanship in many places. Indeed, several states have moved to independent redistricting commissions, as I profile in a new book , thanks to the hard work of "democracy champions" advocating for nonpartisan reforms, all in an effort to remove politics from the process of allocating representatives. The citizenship question inappropriately inserts politics into the very data that goes into redistricting, moving up the political maneuvering even earlier in the process.

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Three federal courts have already struck down the citizenship question, ruling that the Trump administration could not adequately justify the reasons for the question. The Supreme Court will weigh in soon. The legal issues are somewhat separate from the political ramifications. But either way, shouldn't our elections depend on the best candidates and the best ideas winning, and not the rules of the game? That's what a fair democracy should be all about.

NOTE: This article was updated to clarify that noncitizens are disproportionately members of minority groups.