No, you can't tell who is voting, only who has registered and then do the infamous (usually wrong) exit polls
http://elections.gmu.edu/Early_Voting_2008_Final.html
According to this, 25% of votes caste in ohio in 2008 were early votes. Ppp is basically saying this number has already been met 3 weeks out from the election. Seems both astonishing and ludicrous.