"There's not much bang for the buck," says John Geer, a political science professor at Vanderbilt University who studies presidential campaign advertising. "The public is pretty much set on who they will vote for and only a tiny slice is up for grabs."
That was the finding of his YouGov Ad Rating project, which screens political commercials with representative sample of 600 voters, including an oversample of 200 swing voters, who judge them for their fairness, believability and emotional reactions. Few ads, he said, really "move the dials."
Not that the candidates and their backers aren't trying their best to do just that.
In the final weeks, Obama's team is running an ad warning that Romney would cut Medicaid money for nursing home care. "We have a president who won't let that happen," the ad says.
Romney primarily is running a spot in which he promises to boost the economy through manufacturing, energy and cracking down on China.
"Let me tell you how I will create 12 million jobs when President Obama couldn't," Romney says.
Both sides are being buffeted by independent groups.
Romney is getting a big assist from two super political action committees, Restore Our Future and American Crossroads. The pro-Obama Priorities USA Action is running an ad saying Romney would cut early childhood education if elected.
Among those who aren't watching is Paul Gentille, a 67-year-old Obama supporter from St. Petersburg.
He said he tuned out the ads months ago. "Everyone I know has already made up their mind. The ads are kind of annoying," he said. "It's a shame to see so much money being spent."
On the other side is Julie Harris, also of St. Petersburg.
The 33-year-old stay-at-home mom said she always planned to support Romney and that his ads made her "more enthusiastic" about doing so. One particular Obama ad stuck out to her: the ad assailing Romney's pledge to end federal support of public television and the Sesame Street character Big Bird. Even though she's a fan of public TV, she says that ad won't affect her vote.