AUDIE CORNISH, HOST:
From NPR News, this is ALL THINGS CONSIDERED. I'm Audie Cornish.
ROBERT SIEGEL, HOST:
And I'm Robert Siegel.
If you thought the presidential primaries were remarkably negative, well, statistical evidence now says you're right. A new analysis of TV ad finds that 70 percent of the messages were negative.
NPR's Peter Overby reports that behind that number was a crowd of heavily-finance superPACs throwing elbows on behalf their candidates.
PETER OVERBY, BYLINE: Now that Mitt Romney has locked up the Republican nomination, the pro-Romney superPAC, Restore Our Future, is on the air with a positive that it's used before. It's a story of how a 1996, Romney helped to find the missing daughter of a former colleague, Robert Gay.
(SOUNDBITE OF A POLITICAL AD)
OVERBY: Romney put his employees to work on the search in New York City. The girl was found in a suburban town a few days later.
That ad is a rare bright spot in a campaign marked by snarling attacks and sneering contrasts. Seventy percent of the presidential ads have been negative this cycle, versus 91 percent positive at this point in the 2008 election. That's the new analysis from the Wesleyan Media Project, which examines political ads on broadcast TV and national cable. The raw data come from Kantar Media.
One of the Wesleyan Project's co-director is Erika Franklin Fowler, a political scientist at Wesleyan University in Connecticut. She says that at this point in the 2008 cycle, 97 percent of the ads came from candidates. But this cycle...
ERIKA FRANKLIN FOWLER: Sixty percent of all ads are sponsored by interest groups, which is really, truly a historic number.
OVERBY: The shift follows the Supreme Court's 2010 Citizens United ruling and a subsequent lower court ruling which encouraged outside groups to plunge into the presidential contest. Fowler says that for the candidate it's worked out great.
FOWLER: As candidates, you do want to outsource some of the negativity if you believe that there is going to be a backlash for going negative. And there is some evidence in political science to suggest that the backlash will be a little less if a negative ad is sponsored by an interest group, as opposed to being sponsored by a candidate.
OVERBY: The superPACs accounted for 83,000 primary campaign ads, according to the Wesleyan Project. That's significant because superPACs have to disclose their donors. But in the general election campaign, groups that don't disclose their donors have already run more than 35,000 ads.
Bowdoin College Government Professor Michael Franz is another co-director of the Wesleyan Project. He says superPACs tend to get their money from people close to the candidate. But donors to the non-disclosing groups are different.
MICHAEL FRANZ: They're not as explicitly tied to a candidate as they are to a particular party winning the White House.
OVERBY: And he says these general election donors have bigger agendas.
FRANZ: The stakes are a little higher, so not having to disclose donors becomes more valuable.
OVERBY: So far, in the general, the top advertisers are President Obama's re-election campaign, the Democratic National Committee, and two conservative groups - Crossroads GPS and Americans For Prosperity. The pro-Obama operation, which discloses its donors, has aired more than 20,000 ads so far. The two conservative groups, whose donors are anonymous, have run about 24,000.
Peter Overby, NPR News, Washington.