from your site:
That's fine, but regarding districts such as IL-15, IL-18, IN-9, PA-12 that are so close (and have missing counties), what process do you use to predict them voting a certain way?
For the finer details, I'll actually have to suggest that you contact Crisitunity (his e-mail is on the sidebar of the site), since he might not see a comment in the post given how old it is. I think, though, that in the case of the very tiny counties (or, more likely, the tiny bits of counties), those are simply left out rather than predicted.
So if , say, 200K people voted in a race and one part of one county accounts for 200 registered voters, that will barely show up in the tenths of a percent. Given that this cannot be a perfectly exact exercise for a number of reasons, it's probably safe only to view most of these numbers as accurate to whole percentages.