Justin Levitt in the Washington Post's Wonkblog (AP Photo/Rogelio V. Solis):
Requirements to show ID at the polls are designed for pretty much one thing: people showing up at the polls pretending to be somebody else in order to each cast one incremental fake ballot. This is a slow, clunky way to steal an election. Which is why it rarely happens.
I’ve been tracking allegations of fraud for years now, including the fraud ID laws are designed to stop. In 2008, when the Supreme Court weighed in on voter ID, I looked at every single allegation put before the Court. And since then, I’ve been following reports wherever they crop up.
To be clear, I’m not just talking about prosecutions. I track any specific, credible allegation that someone may have pretended to be someone else at the polls, in any way that an ID law could fix.
So far, I’ve found about 31 different incidents (some of which involve multiple ballots) since 2000, anywhere in the country. If you want to check my work, you can read a comprehensive list of the incidents below.
To put this in perspective, the 31 incidents below come in the context of general, primary, special, and municipal elections from 2000 through 2014. In general and primary elections alone, more than 1 billion ballots were cast in that period.
Some of these 31 incidents have been thoroughly investigated (including some prosecutions). But many have not. Based on how other claims have turned out, I’d bet that some of the 31 will end up debunked: a problem with matching people from one big computer list to another, or a data entry error, or confusion between two different people with the same name, or someone signing in on the wrong line of a pollbook.
More here.