I know candidates spend more each year, but that seems to be due to the fact that most of politics is bullshit, and most campaign consultants are chosen more for their contacts than their ability. Seriously, go look at the research on campaign advertising and changing people's opinions. For example this was a pretty groundbreaking study when I was at UC San Diego:
http://fas-polisci.rutgers.edu/lau/articles/LauEtAl_EffectsOfNegativePoliticalCampaigns.pdf
Sadly, I am willing to bet that most campaigns would not shy away from airing a campaign ad with a 'pants on fire' tag. The percentage of people viewing the ad that would actually take the time to check the website would likely be exceedingly small, and generally they would be the ones most skeptical of the message anyway.
This doesn't mean that more effective and honest TV ads would have no effect, but I find it unlikely that they will have anywhere close to the effect that some here might expect.