[T]he study shows is that the polling firm Greenberg Quinlan Rosner went back at the end of 2008 and looked at who in their samples actually voted. It turned out that something like 87% of people who said they were likely to vote ended up voting. 70% of those who said they [were] pretty likely voted. But 55% of people who said they were unlikely to vote, and got kicked off polls because of that, ended up voting.
interview with Dylan Matthews