This presidential election is being concentrated on 19, 20 battleground states. There's 210 media markets in the United States and we're seeing advertising in only 93 of those media markets, and that translates into only 40 percent of Americans being potentially exposed to television advertising and 60 percent of Americans, those Americans who live in big states like California, Texas and New York, not seeing any political advertising at all.[pbs]
The press release [pdf], available at the Wisconsin Advertising Project home page, includes several graphs and analysis of the results of the survey.