The U.S. Supreme Court on Monday handed Democrats a major victory in the redistricting wars.

A unanimous court ruled in Evenwel v. Abbott that states must use total population rather than registered voters to draw district lines. The ruling maintains current practice and is seen to help Democrats, especially in fast-growing communities with large numbers of minorities and immigrants.

Moving to only using registered voters would have put greater emphasis on whiter suburban areas with higher concentrations of voters.

But Monday's ruling expressed no opinion on whether a state may adopt such a rule, if it chooses. That explains why all the justices could agree on the outcome.

And the Washington Post notes the case was brought to challenge Texas' policy of using total population:

The Project on Fair Representation has challenged Affirmative Action cases in the past. Its leader, Edward Blum, told The Post's Robert Barnes that drawing districts based on eligible voters is just more equitable.