WASHINGTON — The Supreme Court opened the door Monday to state laws that require voters to show a photo identification before casting a ballot on election day. The ruling is a clear victory for Republicans, who have pushed for such laws to combat election fraud, and comes over the objections of Democrats, who say the requirements make it too hard for some people to vote.
The effect on the 2008 presidential election may be limited because strict voter ID laws are in effect in few states -- Indiana, Arizona, Georgia and Florida among them. Some states have more lenient rules, and half -- like California -- have no ID requirement on election day.
The 6-3 decision upheld Indiana's voter ID law, the nation's strictest, against a challenge from those who predicted it would deter thousands of poor, disabled and elderly people from voting. But the plaintiffs failed to show that even a single voter had been blocked from exercising his or her rights in Indiana because of the 2005 law. The lapse probably doomed the legal challenge.
Justice John Paul Stevens, speaking for the court, said voter fraud was not unheard of in the nation's history. An election day requirement that voters confirm their identity is "amply justified by the valid interest in protecting the integrity and reliability of the electoral process," he said.
Most states with voter ID laws make it easier for people to comply by allowing them to furnish alternative forms of identification -- such as a Social Security card, a utility bill or a student ID.
But voting rights advocates say the existence of such laws could cause many eligible voters to stay home if they do not have an up-to-date driver's license, a passport or another government-issued ID card.
Stevens said that number appeared to be quite small because an estimated 99% of Indiana's population had the necessary ID cards, according to the judge who tried the case.
In dissent, Justice David H. Souter said that meant as many as 43,000 Indiana residents lacked the required ID cards. If they want to vote, they must go to the county seat with a birth certificate.
"A significant number of state residents will be discouraged or disabled from voting," Souter said.
Since the presidential election in 2000 resulted in a deadlock in Florida, both parties have fought hard -- in state legislatures and in the courts -- over election rules.
The Democrats have said states should make it easier and more convenient for residents to register and to vote. In most states, residents must register to vote well in advance of election day. They can show up and cast a ballot after a poll worker has confirmed their name and address. Some states also require voters to sign the register to verify their identity.
Republicans, arguing that such registration systems are prone to abuse, say photo ID rules are needed to deter fraud.
(Republicans, however, were unable to point to a single instance in Indiana of a person posing as another in order to cast a ballot.)
Indiana's photo ID law does not apply to those who cast ballots by mail, and many experts say it would be much easier for voters to cast duplicate ballots that way.
Three years ago, shortly after the Indiana Legislature adopted its ID law on a party-line vote, the state's Democrats and the American Civil Liberties Union sued. They contended the law was unconstitutional because it put an undue burden on the right to vote, at least for some residents. They did not, however, cite people who had been prevented from voting.
A federal judge and a U.S. court of appeals in Chicago, on a 2-1 vote, rejected the lawsuit. The judges noted that people who fly on airplanes must present a photo ID.
A dissenting judge replied that many poor people did not travel on airplanes, and he called the state law a "not-too-thinly-veiled attempt to discourage election day turnout by certain folks believed to skew Democratic."
Because at least 20 states have some form of voter ID law on the books, the Supreme Court agreed to hear the Indiana case to resolve the legal dispute before the 2008 presidential election.
Stevens acknowledged the Indiana law might well have been "motivated by partisan concerns," but that alone was not enough to make it unconstitutional, he said. The challengers failed to show the voter ID requirement would pose a "severe burden" for many voters, he said.
His opinion did not close the door to a future legal challenge if it could be shown that eligible voters were deterred from voting.
Chief Justice John G. Roberts Jr. and Justice Anthony M. Kennedy joined the Stevens opinion.
Justices Antonin Scalia, Clarence Thomas and Samuel A. Alito Jr. said they would have gone further and ruled that voter ID laws were "eminently reasonable," regardless of whether they had an effect on many voters.
Justices Ruth Bader Ginsburg and Stephen G. Breyer joined Souter in dissent.