TAMPA — With swing-state denizens facing 10 more weeks of campaign ad bombardment, the conservative advocacy organization Americans for Prosperity may be cutting through the clutter most effectively with its relatively low-key attacks on President Obama.

That, at least, was the clear verdict offered by 23 Florida voters on Sunday during a focus group convened by Republican pollster and strategist Frank Luntz.

Almost everyone in the group said they voted for Obama in 2008, but they were about evenly split between Obama and Mitt Romney in the 2012 race, with several still undecided.

Luntz showed the group more than a dozen negative TV ads funded by both presidential campaigns and outside groups and asked participants to rate on a scale of zero to 100 the impact of each ad, regardless of which candidate they are leaning toward.

A majority pointed to a 60-second AFP spot — which has been running in swing states as part of a reported $27 million advertising blitz by the Koch brothers-backed group — as the most effective ad of the current cycle.

In the ad, voters who cast their ballots for Obama four years ago speak directly to the camera about why they would not make the same decision in 2012. “He said he was going to cut the deficit in his first term; I’ve seen zero interest in reducing spending,” one man says. “He inherited a bad situation, but he made it worse.”

The ad made an especially strong impression on registered Republicans in the Luntz focus group, but registered Democrats and participants who said that they intended to vote for Obama again also gave it high marks.

Asked what they liked about it, several cited the relatively subdued tone and the effectiveness of featuring “real people” instead of actors or politicians.

“They basically said exactly what I’m thinking,” one of the participants said of those featured in the ad.

“I can almost see myself in that ad,” another added. “It seemed the most real.”

One female voter in the ad praises Obama as a “great person” but in the same breath questions his ability to lead the country.

It’s a line of thought that Romney himself often echoed until recently and one that seemed to make a strong impact on the participants in Tampa, many of whom expressed continued personal admiration for the president during the two-hour session.

“They’re telling you not to vote for Obama pretty much, but it’s not in a personal, negative way,” one focus group member said of the ad’s approach.

Luntz told a small group of journalists who watched the proceedings from behind a one-way mirror that the AFP ad has been deemed the most effective by every focus group he has conducted around the country in recent months.