The Supreme Court agreed Tuesday to hear an important case about whether states must count only those who are eligible to vote, rather than the total population, when drawing electoral districts for their legislatures.

The case from Texas could be significant for states with large immigrant populations, including Latinos who are children or not citizens. The state bases its electoral districts on a count of the total population, including non-citizens and those who aren't old enough to vote.  

But those challenging that system argue that it violates the constitutional requirement of one person, one vote. They claim that taking account of total population can lead to vast differences in the number of voters in particular districts, along with corresponding differences in the power of those voters.

A ruling for the challengers would shift more power to rural areas and away from urban districts in which there are large populations of immigrants who are not eligible to vote because they are children or not citizens. Latinos have been the fasting growing segment of Texas' population and Latino children, in particular, have outpaced those of other groups, according to census data.

"And because urban areas are more Democratic, the ruling could help Republicans," said Richard Hasen, an expert on election law at the University of California-Irvine law school.

The Project on Fair Representation is funding the lawsuit filed by two Texas residents. The group opposes racial and ethnic classifications and has been behind Supreme Court challenges to affirmative action and the federal Voting Rights Act.