The Justice Department moved Monday to block Texas's new law that requires voters to display government-issued photo identification while voting, arguing the legislation disproportionately harms Hispanic voters.

Republicans are saying the decision was purely political, arguing voter ID laws are intended to prevent voter fraud at the polls. But the Obama administration said in a letter to the Texas Secretary of State that there wasn't evidence of pervasive voter fraud under the state's existing laws.

"The state’s sole justifications for changing the current practice to require photographic identification to vote in person that appear in the legislative proceedings and are presented in its submission are to ensure electoral integrity and deter ineligible voters from voting. At the same time, we note that the state’s submission did not include evidence of significant in-person voter impersonation not already addressed by the state’s existing laws," wrote Assistant Attorney general Thomas PerezThomas Edward PerezClinton’s top five vice presidential picks Government social programs: Triumph of hope over evidence Labor’s 'wasteful spending and mismanagement” at Workers’ Comp MORE.

Instead, the Obama administration argued that the legislation was designed to make voting harder for minorities and the poor, who are least likely to hold a government-issued ID.

"Even using the data most favorable to the state, Hispanics disproportionately lack either a driver’s license or a personal identification card issued by DPS, and that disparity is statistically significant," Perez writes.

Republicans plan to challenge the Justice Department's ruling in federal court, arguing that the legislation contains specific exemptions for the elderly, poor, and those who held religious objections to being photographed. Under the law, the state would provide free voter ID cards for those unable to afford driver's licenses or state ID cards.

House Judiciary Committee Chairman Lamar Smith (R-Texas) defended the legislation Monday, noting citizens are required to show I.D. in order to open a bank account, drive a car, or board a plane.

"This is an abuse of executive authority and an affront to the citizens of Texas. It’s time for the Obama administration to learn not to mess with Texas,” Smith said in a statement.

Sen. John CornynJohn CornynRussians' indictment casts shadow ahead of Trump-Putin summit Top GOP senator: Trump should be 'clear-eyed' going into meeting with Putin Doug Jones walks tightrope on Supreme Court nominee MORE (R-Texas) accused the president of wielding the Justice Department as a political tool.

“Voter identification laws are constitutional and vital to protecting the integrity of the democratic process," Cornyn said in a statement. “Today’s decision reeks of politics and appears to be an effort by the Department of Justice to carry water for the President’s reelection campaign.”

The Justice Department has power under the Voting Rights Act to halt voting laws or redistricting actions in 16 states because of a history of voter-rights violations. Eight states have passed voter ID laws in the past year, and an Indiana law was upheld by the Supreme Court. But a similar measure in South Carolina - one of the states that also undergoes additional scrutiny for changes to election law - was blocked in December.

“The U.S. Supreme Court has already ruled that voter identification laws are constitutional,” Texas Attorney General Greg Abbott said in a statement. “Texas should be allowed the same authority other states have to protect the integrity of elections. To fast-track that authority, Texas is taking legal action in a D.C. Court seeking approval of its voter identification law.”

But Democrats note that to receive the free voter's cards, applicants would have to provide original copies of birth certificates or other identifying documents that themselves carry cost, both financially and in time to obtain.

The issue has become a hot-button topic in the states. While campaigning in South Carolina, GOP presidential candidates frequently praised the legislation. South Carolina Attorney General Alan Wilson, defending his state's measure, told the Justice Department that it appeared "over 900 persons who were deceased at the time of the elections had voted."

A State Election Commission review of 2010 elections found that number was likely exaggerated, the byproduct of clerical or poll workers' errors rather than widespread election fraud.

This post was updated at 1:55 p.m.