State Rep. Joaquin Castro announced he would run for the same House seat as nine-term Rep. Lloyd Doggett in Texas, setting up a divisive Democratic primary.

Castro told the Associated Press on Friday the district has “incredible potential.” “This would be among the few Congressional districts in the nation that connects two major American cities,” he said.

Republicans in the state Legislature passed a new Congressional map this month that moved Doggett into a much more conservative district. Instead of running there, Doggett opted to run in the neighboring, newly drawn 35th district, which stretches from south of Austin to San Antonio.

Castro’s announcement signals Doggett will have company — and stiff competition — for the seat. The Castro name is well-known in the area because his twin brother, Julian, is mayor of San Antonio.

“Though Mr. Castro has not represented this district, he is apparently seizing this Republican-created opportunity instead of running from his own state legislative district to help us regain the majority,” Doggett said in a statement.

The new Congressional map awaits GOP Gov. Rick Perry’s signature. However, the courts are expected to have the final say over the newly drawn House districts. Democrats have already filed a lawsuit protesting the map, and the Department of Justice must rule that it adheres to the Voting Rights Act before it can take effect.