By Patricia Zengerle and Steve Holland
WASHINGTON/TAMPA, Florida (Reuters) - Is Mitt Romney an out-of-touch elitist and bully who led a rapacious business that killed common folks' jobs?
That portrayal of the presumptive Republican presidential candidate is the most frequent one painted by President Barack Obama's campaign and its allies, but their line of attack has yet to hit home.
The former Massachusetts governor is rising in the polls, including a Gallup survey this week that showed 50 percent of Americans now have a favorable opinion of him, the highest yet.
Part of that may be due to a honeymoon effect for Romney as Republicans rally now that he has effectively clinched the party's nomination.
It could also be a sign that Democrats' attacks on him for cutting blue-collar jobs when he was head of the Bain Capital private equity firm have not resonated with voters as much as they had hoped.
"To some extent, Romney's been inoculated against them," said Republican strategist Matt Mackowiak.
A Fox News poll this week that showed Obama leading Romney overall nevertheless put the Republican ahead on handling of the U.S. economy and creating new jobs.
For three straight days this week the Obama campaign, its Super PAC group, and Vice President Joe Biden attacked Romney's jobs record at Bain, focused on the company's closure of a Kansas City steel mill it had acquired.
Bain acquired Worldwide Grinding Systems, a steel mill in operation since 1888, in 1993. A decade later, the bankrupt mill was padlocked and some 750 people lost their jobs. Workers were not given the severance pay or health insurance they'd been promised and their pension benefits were cut.
The Democrats' strategy is to strike at the heart of Romney's campaign: his message that business experience makes him better placed than Obama to bring down the jobless rate.
Attacks like those may begin to take a toll on Romney but, for the moment, he is withstanding them.
"I think these become less effective as you continue to pound away at them. If you trot out 1,000 people who may have lost their jobs in a situation where (Bain) were trying to make a company profitable, does that 1,001st person have as much of an impact as the first?" Mackowiak said.
Romney's campaign was quick to reply to a video from the Obama re-election team on the Kansas City mill, releasing a clip of its own within hours that featured another steel plant that had succeeded with Bain's help.
Romney has learned from failed campaigns for a Senate seat in 1994 and the Republican presidential nomination in 2008 that he will hear about Bain from critics.
"This line of attack happened in '94," said a senior Romney adviser. "It happened in '08 and this line of attack happened a few months ago. If we weren't ready for this line of attack I would say probably someone should be shot for malfeasance. Everyone knew it was coming."
The Democrats' aim is to build a narrative to define Romney as an elitist over the next six months not just a few weeks, said Rodell Mollineau, president of American Bridge 21st Century, a pro-Democratic research group.
"If you are just yelling that one time, then it gets lost through all the noise. It's a whisper in the wind," he said. "But if you find ways over and over and over again through different messages, tactics, press conferences ... whatever means you can find, then that criticism's going to grab hold."
Romney's bump in the polls - led by a CBS News/New York Times survey that had him ahead of Obama by three points - could be a temporary surge as Republicans climb on board his campaign after his main opponents in the party dropped out of the primary race in recent weeks.
"The spike in Romney's favorable rating ... is predictable, given that he has become the presumptive Republican nominee," wrote Jeffrey M. Jones of Gallup. "Presidential candidates typically get a spike in their favorable ratings in the wake of winning the nomination."
Obama still leads Romney on Gallup's favorability rating by 52 percent to 50 percent, although the two men are tied in a matchup over who would make the best president.
BAIN STRATEGY COULD BACKFIRE
Romney is struggling to stay on his economic message, as Obama has dominated the news cycle since the general election contest started two weeks ago, visiting Afghanistan on the anniversary of Osama bin Laden's killing and making a landmark announcement of support for gay marriage.
He said the Obama campaign was using the Bain criticism to mount a "character assassination" of him.
"My effort at Bain Capital as you know was in every case designed to try and make the enterprises that we invested in more successful," he said in Florida on Thursday.
"And the purpose of the president's ads are not to describe success and failure but somehow suggest that I'm not a good person, not a good guy, and I think the American people will know better than that, if they don't know already," he said.
The Bain strategy has a familiar ring to it for those who already tried to tar Romney with the issue and failed.
Fellow Republican Newt Gingrich, whose supporters put out a 28-minute video during the South Carolina primary in January depicting Romney as a corporate raider, regretted the attacks, said Gingrich senior adviser Bob Walker.
"We wanted to emphasize Newt's strong credentials as the best candidate to beat Obama and emphasize the economy," Walker said. "We ended up doing three or four days discussing Bain. I would actually contend it was harmful to us."
Gingrich won in South Carolina, but was trounced by Romney in Florida a week later, and Republicans railed against Gingrich for sending what was seen as an anti-business message.
Democrats are betting that the Bain ads will resonate better with the wider populace in the general election than with Republican primary voters.
One criticism of Romney that does appear to be dying out is the accusation that he bullied a boy at his high school in the 1960s who was presumed to be gay.
A Reuters/Ipsos poll this week showed only 53 percent of Americans had heard of the incident and 28 percent said they viewed Romney less favorably because of it.
(Editing by Alistair Bell and Todd Eastham)