I really hate the commericals. I think the money is better spent getting out the vote on the ground and organizing fundraisers/rallies on the local level. It seems to me that at this point in the game if anyone is deciding their vote in October based on a commercial they see they are in the minority.
I find it hard to understand myself but if you look at the exit polls, a significant percentage of people make up their minds in the last week and last three days before the election. That percentage is generally greater than the margin of victory.
So campaigns spend more and more money to convince fewer and fewer people as time goes on. And, paradoxically, many elections are decided by the least politically engaged, least informed, and least partisan. Go figure.