Reprinted from Constitution Daily, the blog of the National Constitution Center in Philadelphia.  Post by Lyle Denniston.

Few constitutional issues over the right to vote divide the nation’s two dominant political parties more deeply than the question of whether elections would be fairer if every voter had to show a photo ID before casting a ballot, in person or in the mail. Republicans seem sure that there is a great deal of impersonation going on, so voter fraud is a serious problem. Democrats are equally sure that there is no real problem of fraudulent voting, and that ID requirements are simply a Republican tool to make it harder for Democratic voters to take part in elections.

The Supreme Court has not taken sides on whether there is a partisan motive behind such laws, but the last time it looked at the constitutionality of the voter ID issue, in 2008, its majority did accept that voter impersonation was one possible justification. In that decision, the Court rejected, by a vote of 6-to-3, a claim that the Indiana voter ID law could not ever be constitutional, no matter how it was enforced in an actual election. (That kind of wholesale constitutional challenge to a law is the hardest one to make, so it seldom succeeds.)

Much has happened in the seven years since that decision in the case of Crawford v. Marion County Election Board. The Obama Administration, persuaded of the Democratic perception that voter ID laws are designed to keep minority voters (inclined to vote Democratic) away from the polls, has mounted a series of lower-court challenges to those requirements.

The most activity, however, has come in legislatives, especially after Republicans gained majorities in both houses of those bodies. At the time of the Supreme Court’s decision in the Indiana case, only one other state – Georgia – had a photo ID requirement. Since then, 17 more states have written such laws into their books, and last year, some 14 other legislatures considered such measures. Challengers to such laws say it is no coincidence that the spreading interest in such measures followed sweeping victories for Republican in state legislative elections, in 2010 and again in 2014.

So far, the most sweeping court victory the challengers have won against such a law was the ruling last year by a federal judge in Texas.   Finding that some 600,000 Texas voters, mainly minority voters, would not have the kind of ID that would qualify, the judge found the law intentionally aimed at discriminating against those voters.

That ruling, however, was put on hold by a federal appeals court while an appeal by the state of Texas goes forward. And, last October, not long before the November elections, the Supreme Court split 6 to 3 as it declined to block the law from taking effect. (Justice Ruth Bader Ginsburg famously stayed up all night writing a five-page dissenting opinion, joined by Justices Elena Kagan and Sonia Sotomayor.)

The constitutional issue returned to the Supreme Court in January, when challengers filed an appeal to test the Wisconsin voter ID law, enacted four years ago.   They filed the case of Frank v. Walker, contending that the Wisconsin restriction was more limiting than the one the court had considered seven years ago in the Indiana case. They cited evidence that perhaps 300,000 voters, mainly black and Latino voters, would not have the kind of ID’s that the law requires.

They were heartened because a federal appeals court judge who had written the opinion upholding Indiana’s law, Circuit Judge Richard Posner, had changed his mind when the Wisconsin law came before his court, and filed a dissent as a majority of his colleagues found no constitutional problem with what Wisconsin’s legislature had done.

The appeal went to the Supreme Court for consideration at a private conference last Friday. And, after taking just that one look at the case, the Justices on Monday simply refused to hear it. One possible explanation was that the Wisconsin Supreme Court, after its law had been upheld in lower federal courts, issued a new ruling mandating that the state make photo IDs available free to those voters who did not have them. The Justices had been told of that change by lawyers for the state of Wisconsin, and it could have persuaded them that there will actually be no problem with the law with that change.

Even so, challengers decided on Monday to start a new court case, to try to head off enforcement of the law in future elections. Wisconsin has a primary election early next month, but that would be too soon, state officials said, to put the voter ID requirement into effect. But they argued that the challengers’ case was now over, so the law had survived – at least for that round.

Challengers have been watching the pending case in a federal appeals court against the Texas law. That could be the next one to make it to the Supreme Court, perhaps before the elections in 2016.