WASHINGTON (CNN) -- The Supreme Court on Monday backed Indiana's law requiring voters to show photo identification, despite concerns thousands of elderly, poor and minority voters could be locked out of their right to cast ballots.
Indiana can require voter identification for next month's presidential primary, the Supreme Court ruled.
The 6-3 vote allows Indiana to require the identification when it holds its statewide primary next week. It also will give most state legislatures time to revise their voter laws for the November elections.
This was perhaps the biggest voter rights case taken up by the justices since the 2000 dispute over Florida's ballots, in which George W. Bush prevailed to gain the presidency.
At issue was whether state laws designed to stem voter fraud end up disenfranchising large numbers of Americans who might lack proper documents to prove their voting eligibility. The case raised important constitutional questions, but also involved race and partisan politics. Watch a report on the ruling »
Writing for the majority, Justice John Paul Stevens said any political issues considered by the state were mitigated by its desire to stop voter fraud.
"The state interests identified as justifications for [the law] are both neutral and sufficiently strong to require us to reject" the lawsuit, he wrote.
But in a toughly worded dissent, Justice David Souter said "Indiana has made no such justification" for the statute "and as to some aspects of its law, it hardly even tried."
Indiana Secretary of State Todd Rokita has conceded the state has never presented a case of "voter impersonation," which the law was designed to safeguard against. The 2005 Indiana law requires that a valid photo identification be presented by a person casting a ballot at a polling stations. Previously, most citizens needed only to sign a poll book to vote.
For those lacking a driver's license or other government-issued photo ID such as a passport, the state provides a free voter ID card, issued through the Bureau of Motor Vehicles.
Even so, Souter said, such a law "threatens to impose nontrivial burdens on the voting right of tens of thousands of the state's citizens."
Justices Ruth Bader Ginsburg and Stephen Breyer also dissented.
Stevens was supported by Chief Justice John Roberts and Justice Anthony Kennedy. Justices Antonin Scalia, Clarence Thomas and Samuel Alito backed the majority, but filed a separate concurring opinion, which called Indiana's law "eminently reasonable."
State and federal courts around the country have issued conflicting rulings on voter ID laws. Such a law in Missouri was found unconstitutional, but similar laws in Georgia, Arizona and Michigan were found to be proper.
Liberal activists claim such measures help Republican candidates by keeping away many voters who might be inclined to vote Democratic, a charge state and national GOP leaders strongly deny.
Lawyers presented conflicting data on just how many voters would be affected. Democrats said as many as 400,000 people in Indiana do not have the required identification to vote, while state officials countered the number was fewer than 25,000, perhaps only several thousand.
The justices were well aware of the political stakes involved. During oral arguments in January, Scalia wondered why the Democrats were the ones filing the lawsuit, saying it should have been individual voters who may have been directly harmed by the law. His questioning suggested he thought this was more about politics than the law.
Stevens candidly noted the "real-world impact" of a statute passed by a GOP-controlled state Legislature and signed by a Republican governor.
State officials claim that voter turnout actually has increased 2 percent since the law took effect.
A key issue for the justices was whether a past pattern of voter fraud would be enough to justify the such remedial steps. Past high court precedent puts a premium on a ensuring voting regulations do not become overly burdensome on the public.
"The real question is does it disenfranchise anyone?" Rokita told CNN. "After six elections in the state of Indiana, the answer has been no. ... That's why the opponents to this keep losing in court."
But Democrats cited cases such as that of Karen Vaughn, who could not vote last November because her driver's license and other vital documents had been stolen in a home burglary, and she was unable to get the necessary papers in time to acquire the free voter ID card. The longtime advocate for people with disabilities had previously used a private bank-issued identification card when voting.
"It just boggled my mind why I would need to go through so many processes," Vaughn said. She blamed Republican lawmakers for "trying to keep folks that are the most vulnerable, trying to keep us from voting, trying to make it difficult."
For her to get the card, she first needed a certified copy of her birth certificate, a new Social Security card and other documents. Because of her physical disability, home health assistants often had to accompany her to the various bureaucratic offices. Vaughn said she spent more than $100 on fees and transportation to get the documents.
"For someone who is on a very fixed income, I am not sure how they could do that," she said.
State laws on voter identification vary widely, with Indiana's and Georgia's considered the most restrictive. The laws' opponents say 23 states do not require identification for most voters when they go to the polls, only those voting for the first time. Almost all states require a photo identification when people first register to vote.
The cases are Crawford v. Marion County Election Board (07-21) and Indiana Democratic Party v. Rokita (07-25). E-mail to a friend