If the Trump administration wins its fight to add a citizenship question to the census, it will clear the way for Republicans to execute a major power grab they’ve sought for years that could entrench their electoral advantage with rural whites while undermining the representation of urban and diverse populations.

While the legal battle over adding the citizenship question, now underway in a federal courtroom in New York City, is burrowing into statistical methodologies and sound survey practices, the practical political impact could be enormous, studies have shown.

On the horizon, if the citizenship question is allowed to stay on the 2020 census, is a giant legal battle over whether states can then use the data it produces to draw legislative districts based on the number of citizens rather than total population. It sounds like a wonky distinction, but it’s one with huge consequences for how Republicans in certain states will be able to consolidate their political power, while diminishing the voting power of communities with significant numbers of non-citizens.

Election law observers expect that this next legal fight over representation is almost a given if the Trump administration is successful in defending the question on the census. A number of far-right Republicans have called for excluding non-citizens from the census count used to allocate representation — including Kansas Secretary of State Kris Kobach, who privately lobbied Commerce Secretary Wilbur Ross to add the question for the purpose of excluding undocumented immigrants from congressional apportionment.

“I am almost certain that there will be, post-2020, some sort of case about this, somewhere,” said Joseph Fishkin, a law professor at the The University of Texas at Austin. “Someone will try to do it, and there will be a challenge.”

Justin Levitt, a Loyola Law professor and Obama-era DOJ alum, said that if this expected attempt to overhaul the electoral playing field is successful, it would be the first time since the Civil War that “there are people here who have to pay taxes, who are subject to the rules of the country, but are not represented.”

“On the practical level, it dramatically impacts groups with sizable non-citizen populations,” Levitt said. “Not all non-citizens are non-white, but many are, and Latino and Asian populations in particular are more likely to have significant non-citizen populations within their midst.”

It’s worth noting, that even before there’s any change sought to redistricting, Republicans will get a major electoral boost just by the census undercount expected to occur if the citizenship question is added. The diminished participation of immigrants spooked by the question – and experts believe that even citizen relatives of non-citizens may be discouraged by it — means that those communities will see their representation shrink, to the general benefit of white, more rural areas of the country.

“If you want to minimize the political representation of a particular group, you can try to make sure that there are fewer of them who are revealed by the census,” said Nate Persily, a professor at Stanford Law School. “Or you can then use the census numbers that are available to you in a way that minimizes their representation.”

With a citizenship question, “you can try to minimize their representation,” Persily said, “both at the data collection phase and at the redistricting phase.”

A study by CUNY-Queens College sociology professor Andrew Beveridge analyzing what would happen if states drew districts based on citizens of voting age rather than total population found that “more than half of all districts would be substantially changed.”

The study was conducted during the 2016 Supreme Court case, Evenwel v. Abbott, brought by conservative activists who sought unsuccessfully to prohibit states from including non-citizens in state legislative redistricting.

“The demographic shift in voting power would also substantially favor increasing the number of Republican-dominated districts,” his report said.

His report specifically analyzed state legislatures in New York, Florida, California and Texas.

“In every instance, redrawing districts using the eligible voter standard would most likely result in a shift from Democratic to Republican elected officials,” it said.

If the 2020 Census does ask respondents if they’re citizens, the next step in this Republican power play would likely be a test case to see if the Supreme Court will sanction citizen-based redistricting. As Fishkin notes, conservative activists might not even need to convince a state government to seek this change.

“Localities do a lot of districting, and it’s very plausible to me that some locality will choose almost to be a test case by using this method of counting only citizens for like, city council districting or some local thing like that,” Fishkin said

Levitt — who was at the Justice Department’s civil rights division during the Evenwel litigation, when it argued against letting states draw districts based on citizens — conceded that the precedent was a “little” all over the map.

“So what happens is the Supreme Court has to make up its mind on whether it’s OK or not,” Levitt said. “And there are more than a few people who are scared about the way it which it will make up its mind.”