I think you may have overanalyzed the ads. I don't see them as changing many votes myself. Sure a marginal seat in NY that is open = Dem victory this year, but one has to know more about the pull and reputation of the candidates on the ground, how they interact with votes, and what the local rags are saying, and whom they endorse, and whether they are Dem or GOP rags in general in the past. Absent that, we go with the polls, the partisan history, the wave, and the money tree. That is usually enough, except when it isn't.
OK, you're probably right!