WASHINGTON — The most revealing indicator of the state of our democracy is not to be found in the snowdrifts of New Hampshire but in the marbled chamber of the U.S. Supreme Court. Soon enough, we will discover whether the court under Chief Justice John Roberts will become a partisan tool in the national Republican drive to place constraints on voting that are targeted at those who tend to support Democrats.

Not since the Supreme Court stopped the Florida presidential election recount in 2000 has a voting case been so significant, or so overflowing with partisan bile.

On Wednesday, the justices will hear a challenge to Indiana’s strict law requiring photo identification in order for a voter to cast a ballot at the polls. The state claims the law is necessary to stop voter fraud. Yet no one — not Indiana officials, not the U.S. Justice Department, which has taken the state’s side in the dispute, nor any commission — has come up with a single case in the state’s history in which an impostor showed up and cast a vote.

Never mind. In 2005, Republicans who controlled the Indiana Legislature and the governor’s mansion imposed the toughest photo identification requirement in the nation. Not coincidentally, studies have repeatedly shown that those least likely to possess photo identification — most commonly a driver’s license — are African-Americans, the poor, the elderly and the disabled. In short, they are more likely to vote Democratic. Challengers to the law have identified at least two Indiana voters who have infirmities that make it impossible for them to drive, according to The New York Times. They were prevented from casting ballots and having them counted after years of voting without difficulty.

Though the state set up a way for those without a license to obtain a photo ID, the process is complex, and eligible voters still can be denied. If, for example, a woman produces a birth certificate bearing her maiden name, rather than the married name under which she is registered to vote, she isn’t entitled to the identification. About 60 percent of those who have tried to get alternative IDs have been turned down, according to briefs filed with the Supreme Court.

To make their case before a court that is supposed to decide matters based on the facts and the law, Indiana and its supporters, including the Justice Department, invoke a compendium of allegations of this type of voter fraud or that. Facts seem to be notable for their absence.

The allegations they cite involve mostly news accounts of absentee ballot fraud, inaccurate registration rolls, and even tampering by election officials or poll workers. None of them would be prevented by requiring a photo ID from a voter. None involve an impostor who showed up and claimed to be someone else — the only type of fraud that requiring a photo ID would prevent.

“They’re not only newspaper articles, but they’re generally newspaper articles about allegations that a photo ID law would not prevent,” said Justin Levitt, counsel to the Brennan Center for Justice, which has filed a friend-of-court brief challenging the Indiana requirement.

The Justice Department is a party to this embarrassment, including in its brief an example of absentee ballot fraud in a mayoral primary. But the Indiana ID law has no bearing on absentee voters. The state still allows absentee ballots to be counted without a photo ID, on the basis of a signature checked against registration rolls. Still, the department argues that the mere “temptation” of voter fraud and the possibility of “undetected” wrongdoing is sufficient to support a law that constrains some legitimate voters from casting a ballot in person.

If this sounds remarkably similar to arguments some Republican officials made against certain U.S. attorneys — that they failed to prosecute “voter fraud” cases that turned out to be figments of the partisan imagination — that’s because it is. The voter identification proposals fare best in states where Republicans control legislatures and hold the governor’s office. They have been upheld on the votes of Republican judges, and over the objection of Democratic ones.

Partisan motives are supposed to have no part in the administration of free and fair elections. That is what the United States preaches abroad and what most Americans believed before Florida 2000. We can believe it again only if this Supreme Court rejects the hollow rhetoric of partisans and upholds the rights of all voters.

Marie Cocco’s e-mail address is mariecocco(at)washpost.com.