So far, the 2012 election has been chock full of negative advertising, and most of it has come from innocuous sounding independent groups with names like “Restore Our Future” and “Red White and Blue Fund.” (Names that readers of this site will of course recognize as Super PACs.)

As it turns out, there’s a good reason for campaigns to let outside groups do the punching: It works. Or at least, that’s the conclusion of some new academic research, which finds negative ads from independent groups are more effective than negative ads that come directly from candidates.

In a study published in the political science journal American Politics Research (an earlier non-gated version can be found here), Deborah Jordan Brooks and Michael Murov, both professors of Government at Dartmouth College, find that the attack ads from both sources are equally persuasive. But when the ads come directly from a candidate, they also generate backlash. Since voters dislike negative ads, they lose a little bit of respect for the candidates who endorse the attack. But if the attack ad comes from the independent group, there’s much less backlash against the candidate.

“The fact that the public cannot identify the contributors to so many of these groups thus makes it easier for these groups to go on the attack,” Brooks and Murov write in their article, “Assessing Accountability in a Post-Citizens United Era: The Effects of Attack Ad Sponsorship by Unknown Independent Groups.”

They go on to note that this “helps to explain why negative ads by these groups are now so much more prevalent than in previous eras.”

To test the effects of independent negative ads, Brooks and Murov asked survey participants to judge two fictional candidates for a state assembly race: “Tim Clark” and “Michael Norris.” First, the participants watched positive ads about both candidates touting their “proven leadership,” “knowledge and integrity,” and “common sense approach” and showing footage of the candidates interacting with constituents and working at their desks. Then participants watched an attack ad against Tim Clark. Clark was accused of absenteeism, tax evasion, and “bad debts and campaign violations,” and pictured in black and white photos with ominous music and sound effects.

When the anti-Tim Clark ad was sponsored by Michael Norris, survey participants dropped their favorability of Norris by an average of 0.85 points on a 7-point scale. But when the ad was sponsored by the more anodyne sounding “Citizens for a Better State Government,” Norris’ favorability fell by 0.27 points on a 7-point scale. In other words, there was much less backlash.

Certainly, few voters watch ads in this exact way. But the study does capture an underlying dynamic in how voters respond to these ads, and one that will be further tested with the barrage that is almost certainly still ahead. There may also be cumulative effects that the one-off study does not capture.

According to the Wesleyan Media Project, independent advertising in presidential campaigns is up 1,100% compared to what it was at this stage four years ago, and 86% of that advertising is negative advertising (as compared to 53% of candidate advertising). Overall, 70% of advertising in the current presidential campaign is negative – as compared to just 9% at this stage four years ago. Historically, independent groups are 2.5 times as likely to go negative than candidates.

Better disclosure is one answer, but Brooks and Murov caution that “even increased disclosure will not change the fact that harsh attack ads sponsored by outside entities will tend to be more effective than comparable ads sponsored by candidates, which will tend to enhance the relative power of ads sponsored by independent groups on the airwaves”

In other words, all signs point to a long and vicious season of independent expenditure attack ads. And it’s hard to see the positive side of that.