"Swing voters have judged Obama wanting, but Romney has to show that he's not a typical politician," Luntz said after the session. "There's a sense of betrayal among so many Obama supporters, but Romney can't stick it in their face that they made a mistake. He has to ask if they got what they wanted and would they expect the next four years to be any different."
For the most part, the participants who gathered in an office park near Tampa International Airport credited Obama with trying hard. Some said he was "corrupt" and mentioned the bankrupt Solyndra solar-power company run by campaign donors who got federal loans. Others called Obama aloof and "lost." One man said that the president was "narcissistic."
Romney and Obama are running even in recent Florida polls. The state's 29 electoral votes make it one of the largest prizes on the board.
Luntz's staff said the participants were randomly selected central Floridians who identified themselves as independents - though after a series of questions from him on their recent votes, it developed that the group leaned 57 percent Democratic to 43 percent Republican, in keeping with research showing most self-described independents are more partisan than they think.
Though not as statistically rigorous as polls that analyze hundreds of voters' answers, focus groups have emerged in recent years as a valuable laboratory allowing researchers to drill more deeply into political attitudes.
The participants in Sunday's group were shown TV commercials from both sides - from candidates as well as super PACs supporting them - and given dials to record their reactions on a scale of zero to 100, based on how persuasive they found each ad.
The best-rated ads? Romney's, depicting former Obama voters worried about the future and reluctantly concluding that the president had failed.
"Basically, they are playing on the emotions, what people are feeling," said Khristopher Williams, 34, a transfer agent for a financial company who backs Obama but was moved by Romney's ads.
"It is influencing me," Williams said in the session. "Wow, we did vote for hope and change, but all of a sudden hope is not working, so it's time to try something new."
Later, in an interview, Williams, who is African American, said he could be persuaded to vote for Romney, but only if the candidate reverts to more moderate positions he took as governor of Massachusetts instead of "moving so far to the right."
Luntz said he took away some positives for the Obama campaign.
"They give him credit for trying, and they hate Congress," the veteran pollster said. "Obama has to turn that credit for trying into permission for four more years. It's humble, which he needs to be. He should say, 'America, I ask your permission to give me four more years to keep trying for you.'"
By and large, the group gave Romney high marks for his business experience. Most said they didn't care whether he releases more tax returns - though those who did care were passionate about it.
Several people who were considering a Romney vote said he has to offer more detail on his policy prescriptions. Some said he seemed remote and unfeeling, and the group split on whether Romney's private-equity firm, Bain Capital, contributed to sending U.S. jobs overseas.
"He needs to be more open about his plans," said Linda Compton, 66, a semiretired caregiver for elderly people. "Now, not everyone is a natural-born politician, and he has to work on his charisma. . . . I don't hear genuineness."
Later, Compton said she was almost sure to stick with Obama on Nov. 6 despite her disappointments with him.
Bruce Rademacher of Odessa, who called himself a moderate on social issues but a fiscal conservative, said he wouldn't vote for Obama again.
"When he did have everything going his way for the first two years, Obama delegated leadership to Nancy Pelosi and Harry Reid," Rademacher, 71, a retired bank technology engineer, said. "He didn't show his imprint so much. Now, with a hostile Congress, he doesn't seem to have any ideas left."
Contact Thomas Fitzgerald at 215-854-2718 or firstname.lastname@example.org or @tomfitzgerald on Twitter. Read his blog, "The Big Tent," at www.philly.com/BigTent.