SAN ANTONIO — Texas Republicans are used to playing offense — and winning — but this November in the sprawling 23rd Congressional District, they have a fight on their hands.

Two years ago, Francisco Canseco rode the Tea Party wave to Washington after defeating the Democratic incumbent. Now he faces a challenge from State Representative Pete Gallego, Democrat of Alpine, who has served in the Legislature for 22 years.

The district, larger than Mississippi, stretches from San Antonio to El Paso and encompasses 800 miles of the Texas-Mexico border. It has the distinction of being both overwhelmingly Hispanic (66 percent) and almost perfectly balanced between the two parties.