FACED WITH VOTER ID legislation that would disenfranchise thousands of Virginians, Gov. Robert F. McDonnell is in a quandary. He can veto the bill and incur the wrath of fellow Republicans, or sign it and reinforce the GOP’s image of hostility toward young, poor and black voters.

Mr. McDonnell is all too aware that the bill, passed by Republican lawmakers despite his warning about legislative overreach, is gratuitous at best. That’s why he sent it back to the General Assembly with amendments that would eliminate its most obnoxious feature: a requirement that ballots cast by voters who lack identification be thrown out unless the voters make a separate trek to local electoral offices to prove their identity.

But the General Assembly restored that provision and sent the bill back to Mr. McDonnell, who now faces a decision: Does he want to be known as a partisan street brawler, or as a grown-up who governs with restraint?

An example of the former is freshman Republican state Sen. Thomas A. Garrett Jr. (Louisa). Although he is a prosecutor, Mr. Garrett had no compunction about twisting the facts to make the case that voter fraud poses a dire threat to the commonwealth. In support of that specious claim, he appeared on Fox News the other day citing “literally hundreds of cases” from the 2008 elections “investigated and confirmed” by police. Sounds scary, right?

Unfortunately for Mr. Garrett, the facts, as related by the Virginia State Police, are these: Of more than 5 million registered voters in the state, 400-odd cases of possible registration irregularities were referred to police. Of those, 351 were dismissed as unfounded or thrown out by prosecutors; 26 remain under investigation; and just 38 cases resulted in charges, mostly of providing false information. In other words, less than 1/1000th of 1 percent of the state’s voters were proven to have lied on their registration forms.

Unlike Mr. Garrett, most responsible Virginia Republican leaders acknowledge there is no evidence of systematic voting fraud in the commonwealth. The unavoidable conclusion is that the voter ID bill is a solution in search of a problem — the sort of government meddling that the GOP usually hates.

For decades, Virginia law has allowed voters who lack identification to cast ballots, as long as their names appear on registration rolls and they sign affidavits attesting to their identity. Falsifying an affidavit is a felony, but few criminal cases have been brought because fraud has been so rare.

The real reason Republicans have pushed to change the system is that they hope to inconvenience, and thereby disenfranchise, the 12,000 or so Virginians who lacked IDs when they voted in 2008 — a group, comprised disproportionately of blacks, the poor and young voters, who tilted to the Democrats. Mr. McDonnell is a loyal Republican, but as governor, to his credit, he has so far avoided the ugly partisan warfare that has gripped other state capitals. The voter ID law is a litmus test of principle versus partisanship.