A good question and I can not 100% account for each and every case of vandalization but posts 118806 and 807 the perps were either identified as a Democrat or a supporter of a Democrat and it is safe to assume that the individuals who were putting "happy faces" on a Republican's signs were also supporters/Republicans.Rogue, how do you know that Republicans are not trashing their own signs to attract sympathy, and therefore, votes? It's not a bad strategy, as destroying the opponents' signs is very counter-productive, no? As I just said, it could easily produce the opposite reaction, namely, attract voters.
Now, in the few cases of "racist" signs at TEA Party events the pictures seem to be plants. Most likely by Libtards to. You have a picture (#1) in this Huffington Post picture in which the "TEA Partier" is at the back of the protest, he his showing his sign to the rear (we have no idea what the other side says) which is deliberately facing the cameraman!!! To me it looks like he is a LIBERAL PLANT.
Same goes for picture #6. The other eight pictures are not racist (except in the sick minds of Libtards). Now this picture is, IMHO, RACIST but we do not know who made or posted it.