Halloween has never been my favorite holiday because I get scared easily. However, being in Washington, DC, I am entertained by all of the political nerdy costumes around. Last year (as I described here) I saw people dressed up as Watergate tapes, Janet Reno, Mark Foley-bait, WTO protesters, etc.
This year, I already have friends thinking up costume ideas. For example, my friend from UCLA and nationally known political blogger, Ezra, is dressing up as Jesus with a bong in honor of the big Supreme Court free-speech case about a "Bong Hits 4 Jesus" poster. He also found this site, which has stencils of Presidential candidates for your pumpkin.
The bad part about not picking a candidate is that I do not know who to carve into my pumpkin.