Presidential campaign ads are ubiquitous, but do they work?

A robust television ad campaign is a critical element in winning an election, which explains why the Obama and Romney campaigns and their parties and allies are in the midst of unleashing the most sustained and concentrated blitz of 30-second commercials in American political history.

But for all of the cash thrown at presidential TV ads — perhaps more than $1 billion between now and November — their impact has historically been relatively small in swaying large swaths of voters in the general election.

Graphic

Watch the latest campaign ads and track ad spending

“The most fundamental point about political advertising is that it matters at the margins,” said Erika Franklin Fowler, director of the Wesleyan Media Project, which tracks and analyzes campaign ads. “It might help in a close election,” but factors such as the state of the economy and partisan identification are much more influential, she said.

But if that is so, it raises a fundamental question: Why do presidential campaigns devote such resources to an effort that allegedly yields so little?

The answer may be that they can’t afford not to.

The risk of losing even a fraction of the vote by being outspent on advertising largely drives the relentless fundraising and spending of both parties, says Travis N. Ridout, a political scientist at Washington State University. “You don’t want to be left behind,” Ridout said. “No one is willing to unilaterally disarm.”

“Ask Al Gore if a small advantage matters,” said Ken Goldstein, president of the ad-tracking firm Campaign Media Analysis Group of Washington, referring to Gore’s 540-vote loss in Florida in 2000.

Local TV advertising will consume about half of all the dollars raised by the candidates, their parties and the independent super PACs that are the wild card in this year’s campaign, Goldstein estimates. That means at least $1 billion will be spent on TV spots in just a dozen or so swing states that could determine the election. Others guess more — lots more: Bill Burton, a former aide to President Obama, told New York magazine last month that the total raised this year could top $2.6 billion, with much of that total ticketed for advertising. with two-thirds of that ticketed for advertising.

Fundraising figures released by Obama and Republican contender Mitt Romney last week haven’t challenged the most-expensive-election-ever narrative. Romney and his party raised more than $76 million last month, outdrawing Obama and Democrats, who hauled in $60 million. Romney is also getting help from Republican-leaning super PACs that have raised far more than their Democratic-leaning counterparts. (Advertising strategists for Romney and Obama declined to comment for this article).

The notion that all that TV money will buy relatively little is almost as old as TV itself. Dozens of academic examinations since the 1940s have shown that TV ads have limited persuasive effects on voters in general elections, often accounting for no more than a 1 or 2 percent difference, and often considerably less.

What’s more, outspending a rival on advertising in a general-election campaign doesn’t guarantee anything; John Kerry and his Democratic allies ran almost 200,000 more commercials than George W. Bush did in 2004 and lost in a close election. On the other hand, Obama had a narrower advertising advantage over Sen. John McCain in 2008 and won relatively easily.