I'm down in the records as a reliable Democratic vote. (Read The Victory Lab for an interesting take on how well the experts can track and manipulate such data.) So usually I get a call during Election Day to be sure I've voted, perhaps a call or two before to be sure I'm planning to vote. This year for the first time I got a call nudging me to early vote. Virginia's rules on early voting are more restrictive than other states, though there are enough exceptions that I could perhaps fit through one of them. The advantage of early voting for the campaign is they'll know when I've voted (that's a public record), so they can scratch me off their list and focus their efforts on others.
That logic and effort is sort of reflected in this Mark Halprin piece on Obama's ground game (hat tip Volokh Conspiracy) and this Molly Ball piece in Atlantic.
[Updated with the last link.]