Attorney General Eric H. Holder Jr. on Tuesday vowed to be “aggressive” in challenging voting laws that restrict minority rights, using a speech in Texas to make his case on the same day a federal court was considering the legality of the state’s new voter ID legislation.

“Let me be clear: We will not allow political pretexts to disenfranchise American citizens of their most precious rights,” Holder said in the speech to the National Association for the Advancement of Colored People. “I can assure you that the Justice Department’s efforts to uphold and enforce voting rights will remain aggressive.”

Holder received a standing ovation as the Houston crowd chanted “Stand your ground!” and “Holder, Holder!” But the attorney general’s remarks drew sharp criticism from Republican lawmakers, who characterized the speech as a political tactic aimed at bolstering President Obama’s reelection prospects.

“It’s very telling that instead of making legal arguments in front of the court, the attorney general is making political speeches more than a thousand miles way,” said Lucy Nashed, a spokeswoman for Texas Gov. Rick Perry (R).

The controversy over voting rights is playing out against the backdrop of a growing national debate over the issue. A three-judge panel of the U.S. District Court in Washington is hearing arguments this week on the Texas’s voter ID law, which requires voters to show a photo ID before being allowed to cast their ballots.

The Justice Department in March blocked the Texas law, which was signed by Perry in May 2011, contending that it would violate the 1965 Voting Rights Act and disproportionately harm Hispanic voters.

“Many of those without IDs would have to travel great distances to get them and some would struggle to pay for the documents they might need to obtain them,” Holder said Tuesday at the 103rd convention of the NAACP. He called the laws “poll taxes,” referring to fees in some states in the South that were used to disenfranchise blacks during the Jim Crow era. Under the Texas law, the minimum cost to obtain a voter ID for a Texas resident without a copy of his birth certificate would be $22, according to the Justice Department. The Texas legislature voted down a proposal to allow people to get the documents needed for a voter ID for free.

Under the Obama administration, the Justice Department has challenged new voter laws across the country, including in December in South Carolina, where the administration argued that a voter identification law would adversely affect black voters. Because Texas and South Carolina have a history of voter discrimination, they must get “pre-clearance” from the Justice Department before any new election laws can take effect.

In all, however, eight states passed voter ID laws last year, including the battleground state of Pennsylvania. Supporters of the measures — seven of which were signed by Republican governors and one by an independent — say they are needed to combat voter fraud. But critics say the new statutes could hurt turnout among minority voters and others, many of whom helped elect Obama in 2008.

In his speech, Holder told the NAACP that the arc of American history has always moved toward expanding the electorate and that “we will simply not allow this era to be the beginning of the reversal of that historic progress.”

The NAACP has launched a campaign against the voter ID laws, and its president, Benjamin Todd Jealous, has compared the fight to the one waged during “Selma and Montgomery times,” a reference to the civil rights movement.

Proponents of the Texas voter ID laws say the Obama administration is infringing on states’ rights.

“This is a case about Texas’s proposed implementation of one of the most popular voting reforms of the last 20 years, a common-sense requirement that when you show up to polls to vote, you prove you are who you say you are with a photo ID,” Texas attorney Adam Mortara told the U.S. District Court on Monday.

Keith Ingram, director of the elections division of the Texas secretary of state’s office, testified that there are potentially 50,000 deceased voters on the Texas voter rolls.

“Why would the Department of Justice not want states to remove ineligible felons, ineligible non-citizens and the dead from their voter rolls?” House Judiciary Committee Chairman Lamar Smith (R-Tex.) asked Holder during a committee hearing last month. “The administration’s actions aren’t just wrong — they are arrogant, undemocratic and an insult to the rule of law.”

On Tuesday, the second day of the federal trial, the judges heard arguments about the impetus behind the Texas law and how many voters might be disenfranchised by the ID requirement. Justice Department attorney Elizabeth Westfall has said that as many as 1.4 million voters could be affected, but a University of Texas statistician testified that the number of voters without an ID was closer to about 168,000.

The arguments are expected to continue through this week and are being heard by Rosemary Collyer, appointed in 2002 by President George W. Bush; David Tatel, appointed by President Bill Clinton in 1994; and Robert Wilkins, appointed in 2010 by Obama.

Rachel Weiner and special correspondents Lindsey Ruta and Annelise Russell contributed to this report.