Federal law says states and localities with a history of discrimination cannot change voting procedures without getting approval from the Justice Department or a federal court in Washington.
Texas today is asking the U.S. Supreme Court to allow use of new, unapproved electoral districts in this year's voting for Congress and the state Legislature.
The outcome could be another blow to a key provision of the Voting Rights Act. Justices in 2009 raised doubts about whether Southern states should still need approval in advance of voting changes -- more than 40 years after the law was enacted.
The legal fight over Texas political maps arises from the state's population gain of more than 4 million people in the 2010 census.