Almost two-thirds of presidential ads on the air between June 1 and Sept. 30 were negative, compared to about 40% during that period in 2008. In 2004, 34% of the ads in that period were negative, while for 2000 the figure was 18%, the report said.
Fewer than 8% of presidential ads on the air between Sept. 9-30 were positive. Ads promoting President Barack Obama during that three-week period dropped from about 28% in 2008 to 2.5% this year. Ads promoting the Republican presidential candidate, Senator John McCain in 2008 and former Massachusetts Governor Mitt Romney this year, declined from 32% to 15%.
"It will come as no surprise to those who have been bombarded with advertising in key markets, but 2012 is another record-setting year in terms of the amount of negativity we're seeing in the presidential race," Erika Franklin Fowler, co-director of the Wesleyan Media Project, said in a news release.
The project is associated with Wesleyan University in Middletown, Conn. The presidential advertising study analyzed data gathered by Kantar Media's CMAG, an ad tracker based in New York.
Wesleyan's report also analyzed the volume of presidential advertising throughout most of September -- and where those spots aired.
Obama's campaign aired 83,080 spots in that time, more than double the Romney campaign's 36 ,406, the report said. It said Obama and Democratic allies supporting him with advertising had more commercials on air in 14 of 15 key markets in swing states, those with a history of voting for either major party nominee in presidential races.
"The heavy Obama advantage may be one reason why polling in battleground states has moved against Romney in recent weeks," Ms. Fowler said.
Only in Las Vegas were Romney and his Republican allies, including the party and several super-political action committees, on air more often.
Priorities USA Action, a super-PAC run by former Obama aides, announced today that it would begin airing ads in Nevada, shifting its money into that state at the expense of markets in Florida and Wisconsin, two larger swing states. An NBC News/Wall Street Journal/Marist College poll last week showed Obama and Romney essentially tied in Nevada.