A tough Texas law requiring voters to show photo identification at the polls discriminates against low-income blacks and Hispanics, a federal court ruled Thursday, wiping out for the November election a measure championed by conservatives and setting up a potential U.S. Supreme Court showdown.

In Washington, a three-judge panel unanimously ruled that the 2011 law imposes "strict, unforgiving burdens on the poor" and noted that Texas' racial minorities are more likely to live in poverty.

It was the state's second major loss in court in three days, coming after a separate federal panel ruled Tuesday that Texas' Republican-dominated Legislature failed to avoid "discriminatory purposes" when drawing new maps for congressional districts and both houses of the state Legislature to reflect Texas' booming population.

"In a matter of two days, the state of Texas has had its dirty laundry aired out across the national stage," said Democratic state Rep. Trey Martinez Fischer, chairman of the Mexican American Legislative Conference. "This deals with the despicable issues of discrimination, voter suppression, these are things that we're not proud of."

The voter ID decision could set a precedent for upcoming legal challenges to similar laws in other states. South Carolina's strict photo ID law is on trial this week in the same federal courthouse.

It also underscores a widespread push, largely by Republican-controlled legislatures and governors' offices, to impose strict identification requirements on voters. But Democrats say fraud at the polls is largely nonexistent and that Republicans are trying to disenfranchise minorities, poor people and college students — all groups that tend to vote Democratic.