A new Republican-drawn congressional map tramples on the rights of Hispanics and blacks in Texas and should be declared illegal, opponents of the plan argued as a federal trial opened Thursday.

Attorneys for the state disputed the allegations from Democrats and minority groups and said the new redistricting plan actually increases minority clout.

Further, the GOP map likely would increase the number of Texas Republicans in Congress, and redress an imbalance, said Andy Taylor, a private attorney representing the state.

Even though most Texans vote Republican — and the GOP holds all statewide elected offices and controls the state House and Senate — only 47 percent of the seats in the state's 32-member congressional delegation are held by the GOP, Taylor said.

Opponents of the redistricting plan — passed during an October special session after lengthy partisan bickering and two boycotts of the Legislature by Democrats — argued in court that the GOP map violates the federal Voting Rights Act (search) and the U.S. Constitution.

A three-judge federal panel is hearing the case in Austin. Testimony from scholars, congressional incumbents and state legislators is expected to take a week or so. Whatever the court rules, an appeal is expected to the U.S. Supreme Court.

Democrats and some minorities challenging the new map want to keep the existing districts that have given Democrats a 17-15 advantage in the congressional delegation.

"There's no reason for us to do the dance again," attorney Anthony Griffin said. "What was the emergency that we were calling special sessions?"

Griffin represents Democratic U.S. Reps. Eddie Bernice Johnson (search) of Dallas and Sheila Jackson-Lee (search) of Houston and is fighting to protect their historically black districts.

Latino voters are caught between the state's two powerful major political parties, said attorney Nina Perales of the Mexican American Legal Defense and Educational Fund (search).

"It's like driving in a small car between two semis on the highway. You've got to keep your foot on the gas and keep going and hope you don't get squashed," Perales said.

Also challenging the redistricting plan are assorted groups of Democrats, some chapters of the League of United Latin American Citizens (search) and the Texas NAACP.