Even though I try to take this sort of information into account myself when I shop, the fact is that I have trouble keeping track of it all.  I've given up worrying about it when I screw up...I just feel good knowing I'm reducing the number of my dollars which end up in Republican hands.  But I'm more far more passionate about my politics than 98% of Americans...do we really expect people to keep up with this enough to make any impact?

As much as I'd like to see every company suffer in direct proportion to the number of dollars they hand to the Republican party, a much more effective response would be to pick some company, some one particularly generous to the Republicans and rightist causes, and do everything in our power to bring them to their knees.  And with that would come the implicit threat that any one else who does the same sort of thing could be next, which would be more effective than any broad-based boycott we could muster.

Companies, in general, donate to political parties as a matter of business, not advertising...in general the public can be counted  on not to notice.  If we were to send a message that a large number of people ARE paying attention, that would have an effect.