As the election approaches, I thought I'd write a little more about the uses of the voter file in this particularly busy time.  It's a very different operation than it is in the earlier stages, when you're setting up your file.  By the time October rolls around, moving as much information into and out of the voter file as possible becomes paramount.  There are a couple of ways that files get used late in the game that don't show up earlier; today, appropos of last night's discussion, we're going to focus on early voting. 

As I wrote earlier, it's too simplistic to say that early voters exactly mirror the general electorate.  But it's also an oversimplification to simply treat early voters as monolithic partisans, either, as Student Redux points out in an insightful comment.  Luckily, the use of voter file data allows us a more fine-grained view of early voting.

Campaigns love their early voters, for a variety of reasons.  First of all, it eliminates uncertainty.  Once your vote is banked, that's it--even if the candidate publically eats a kitten on the Monday before the election, the damage will be limited.  This is especially important for frontrunner campaigns.  Secondly, it conserves resources--states publish information on who has voted early at regular intervals before the election, and once your vote is banked the campaign is free to ignore you.  On a related note, it can be more efficient to activate people for early voting--rather than concentrating all effort on election day, the campaign can spread its effort out over a longer period, and people who vote early often require less commitment of resources to get them out to the polls (for example, highly motivated voters will not need their doors knocked on for reminders).

To fully use this information, campaigns combine early vote information with the other things they know about the electorate.  It might make sense, for instance, to split people along a variety of dimensions--likelihood of voting overall, likelihood of voting early, strength of support for the candidate, and likelihood that the campaign will have to spend resources to get this person to vote.  If a strong partisan is on the Permanent Early Voting list, they might receive less mail and fewer calls; meanwhile, their neighbor, who votes irregularly but has demographic information that makes them likely to vote one way or the other, gets deluged to make sure they turn out this time.  Of course, in order to make sure that the campaign is using this information correctly, it needs to stay on top of updates.  Grabbing as much information as possible about who's voted early is vital to staying on top of the situation; as election day appoaches, speed becomes more and more vital.  Nobody cares if your June 29, 2007 update goes out on June 30; it's a much bigger deal if an October 15, 2008 update goes out a few hours late.

Moreover, as you can see, by this late in the game the voter file has to be integrated fully into almost every arm of the campaign to be used effectively.  Field, voter file, polling, and even small-donor fundraising together can provide more information and do much more to ensure victory than when they're separated.