I had never realized prior to now that ACORN was one of the most powerful organizations in the country. Not only is the group accused of being responsible for the housing bubble and the collapse of the global economy, but it is “now on the verge of maybe perpetrating one of the greatest frauds in voter history in this country, maybe destroying the fabric of democracy.”

At least that’s what John McCain said during the presidential debate last night. I asked Richard Hasen, a professor specializing in election law at Loyola Law School in Los Angeles and author of the Election Law blog, about that line of attack, which is being relentlessly promoted by the G.O.P. and across the right-wing blogosphere.

Here’s what he said (his remarks were lightly edited for length and clarity):

There certainly is some voter-registration fraud, and ACORN’s business model is broken. The people who engage in this sort of thing should be prosecuted. But there is no evidence that fake registrations lead to actual votes being cast on Election Day, certainly not in any numbers that could impact the outcome or threaten the integrity of the process.

Registration fraud can occur when people are employed to turn in voter registration [forms] and they need to turn something in; sometimes they might be paid by the piece. But imagine that you want to steal an election. One way would be to register a lot of individuals using false names, and then send people to the polls claiming to be those voters–and to pay those people even though there’s no guarantee that they will vote the way you want them to. And anyone who does try to vote under a fake name could easily be discovered and charged with a felony.

It makes nice copy to talk about how members of the Dallas Cowboys were falsely registered to vote, but no one is going to turn up and vote under their names.

Another idea going around is that of dead people voting. The idea here is that that you have people looking through the obituaries and sending people to polling places to vote in their names. It’s a stupid way to try to steal an election.

A much smarter way would be to find legitimate voters who will vote the way you want and verify how they voted before you pay them. The actual cases of election fraud that take place fit that model.