WASHINGTON – The Supreme Court has agreed to consider a major shift in how political districts are drawn nationwide by counting only citizens who can vote, not the total population.

If the justices eventually rule for the conservative group that appealed the issue, the decision could dilute the political power of Latinos, especially in large states such as Texas, California and Florida.

The court said Tuesday it will hear the case in the fall and rule early next year.

Since the 1960s, the high court has enforced the "one person, one vote" rule to require that election districts be roughly equal in population. This rule is based on the equal protection clause of the 14th Amendment and it is applied to all election districts, whether for members of Congress, state legislators, county supervisors or local school boards.

At least once a decade, these districts may be redrawn based on new census data. The U.S. Census Bureau seeks to count the total population, including noncitizens and immigrants in the country illegally.

In its appeal, the Project on Fair Representation based in Austin, Texas, says the districts should be balanced based on the number of eligible voters. The group sued on behalf of Sue Evenwel, a leader of the Texas Republican Party. She lives in Titus County in east Texas, where her state Senate district had 533,010 citizens of voting age in 2011. However, another Senate district had 372,000 citizens of voting age.

The appeal in Evenwel vs. Abbott argues that her right to an equal vote is being denied because Texas officials relied on the census data to balance the districts.

Requiring states to switch to counting only citizens will "ensure that voters are afforded the basic right to an equal vote," her lawyers said.

Their appeal noted that same issue arose in Los Angeles County in 1990.

By a 2-1 vote, the 9th Circuit Court of Appeals upheld a ruling that required the County Board of supervisors to redraw its districts and create one with a Latino majority. In dissent, Judge Alex Kozinski questioned the premise of relying on the total population figures, rather than on the count of citizens who were eligible to vote.