WASHINGTON — The Supreme Court cleared the way yesterday for state election officials to require voters to show a government-issued photo identification before casting a ballot.

The 6-3 decision upheld Indiana’s Republican-sponsored voter ID law, the nation’s strictest, against complaints from Democrats that it will deter thousands of poor, disabled, and elderly persons from voting.

At least 20 states require voters to show some form of identification at the polling place, but courts have been split over whether these requirements are constitutional.

Nearly all of these state laws have been sponsored by Republicans who say there is a need to combat “voter fraud.”

Democrats have opposed them just as strongly, arguing they are thinly veiled efforts to discourage some people from voting. For example, elderly and poor people who do not drive a car are less likely to have an up-to-date state identification card.

But the Democrats who sued to block Indiana’s law in 2005 did not name a single plaintiff who had been barred from voting because of the law. That failure doomed the legal challenge.

Justice John Paul Stevens, who grew up in Chicago, said state officials had a legitimate interest “in protecting the integrity and reliability of the electoral process.”

Moreover, he said a judge had found that about 99% of Indiana’s voters had a driver’s license or other identification that would qualify under the state’s law.

Judge Stevens acknowledged the Indiana law may well have been “motivated by partisan concerns,” but that alone is not enough to make it unconstitutional, he said.

The challengers failed to show the voter ID requirement would pose a “severe burden” on many voters, he said.

His opinion did not close the door to a later and more focused legal challenge in the future.

Chief Justice John Roberts Jr. and Justice Anthony Kennedy joined the Stevens opinion. Justices Antonin Scalia, Clarence Thomas, and Samuel Alito Jr. said they would have gone further and ruled that voter ID laws are “eminently reasonable,” regardless of whether they have an impact on many voters.

In dissent, Justices David Souter, Ruth Bader Ginsburg, and Stephen Breyer said the law will pose a burden “on the voting right of tens of thousands of [Indiana’s]citizens and a significant percentage of those individuals are likely to be deterred from voting.”