WASHINGTON (Reuters) - Mitt Romney has secrets. Lots of them, perhaps.
That provocative claim is at the core of President Barack Obama's latest attacks on his Republican rival, a strategy that is dominating the narrative of the presidential campaign and leading anxious Republicans to question Romney's tactics.
In ads, interviews and social-media blasts, the Democratic president's team is casting Romney as a mysterious figure who is guarding important secrets about his wealth and work history.
Feeding the Democrats' storyline: Romney's refusal to release more than a year or two of his tax returns, questions about whether he is being honest about when he left his job at Bain Capital, and the reams of records that have been kept secret from his years as Massachusetts governor and chief of the Salt Lake City Olympics.
The Obama team's tactic - summed up in its new TV ad that asks, "What is Mitt Romney hiding?" - is similar to a Republican strategy that Obama overcame en route to winning the presidency in 2008.
Back then, some conservatives claimed Obama was secretly a Muslim with a socialist agenda who had not been born in the United States, and therefore wasn't eligible to be president.
Obama's 2008 opponent, Republican John McCain, did not embrace such false attacks. He also nixed attempts to blast Obama for ties to a controversial pastor, Jeremiah Wright.
Obama's team, similarly, has made a point of not discussing Romney's Mormonism - even as some analysts are saying that the Democrats' focus on Romney's penchant for secrecy amounts to a subtle reminder of his affiliation with a religion that is mysterious to many Americans.
David Gergen, an adviser to two former Democratic and two Republican presidents, is among those who believe that questions about Romney's faith are an unspoken part of the Democrats' strategy of focusing on the secrecy issue.
"I think they're connected," he said. "Clearly they're trying to weave together: 'Do we really know what he did at Bain ..., do we really understand his faith and, you know, what he would do and who is he?' "
Democrats "know it's in the culture," Gergen said of questions about Romney's religion. "They don't have to say it. I think they're very intentionally weaving these together."
Gergen added that the Obama campaign's strategy could backfire if it mentioned Romney's religion directly.
A COMPARISON TO NIXON
Religion aside, Obama's campaign has taken hold of the secrecy argument against Romney with gusto. It argues that the attacks on Romney are a fair way to punch holes in the Republican's claim that his business experience makes him the most qualified candidate to fix the U.S. economy.
In its attempt to put Romney under a cloud of conspiracy, Obama's team has compared him with former Republican President Richard Nixon, whose devotion to secrecy contributed to his impeachment and resignation in 1974.
Romney's campaign has called the attacks unfair, accused Obama of misrepresentation, and argued that the president is trying to distract from his record on the economy.
But the attacks appear to be getting under Romney's skin, and have led George Will, William Kristol and other conservative analysts to call on Romney to release more tax returns to try to shift the conversation. Some want Romney to change the subject by announcing his choice as a vice presidential running mate.
Instead, Romney has demanded an apology from Obama, a request the president's team has rejected.
Obama's surrogates are now essentially using Romney's complaints about the attacks to cast the Republican as a rich guy who is unaccustomed to being questioned.
"Stop whining," Chicago Mayor Rahm Emanuel, an Obama supporter, said Sunday.
'WHAT IS HE HIDING?'
Conservatives fretting about Romney's response to the barrage of attacks from Obama are focused mostly on the Republican's reluctance to shed more light on his personal fortune, estimated to be up to $250 million.
Unlike most politicians seeking national office, Romney initially declined to release any of his tax returns. In January, under pressure from his opponents in the Republican primaries, he released his 2010 return and an estimate for 2011.
The returns indicated that Romney and his wife Ann held millions of dollars in offshore accounts and once had a Swiss bank account, raising questions about the lengths to which they had gone to avoid paying U.S. taxes.
Now conservatives such as Will, Kristol and Alabama Governor Robert Bentley are calling on Romney to release more tax returns - even if they show, as many suspect, that the Romneys managed to find enough tax shelters to effectively avoid paying any taxes some years.
Some worry that if Romney is so determined to keep his tax returns secret, they must be potentially damaging to the candidate.
"The costs of not releasing the returns are clear," Will said on ABC's "This Week" on Sunday. "Therefore, he must have calculated that there are higher costs in releasing them."
Linda Peek Schacht, professor of political communication at Tennessee's Lipscomb University, said the Obama attacks "will be effective as long as the Romney campaign is handling the response so poorly. The longer they fail to respond in a clear way that puts some of these questions to rest, the worse the damage can be."
She said voters could accept some discrepancies in Romney's record, but not if he does not explain issues such as his keeping money in tax havens such as the Cayman Islands.
"Those are sort of code words or code phrases for, 'You can't trust him; what is he hiding...and why is he hiding it?'"
Obama's team appears to have learned from the 2004 campaign, during which Republican George W. Bush's team used the summer - when many Americans were tuning into the campaign - to define Democratic candidate John Kerry as an out-of-touch elitist. Kerry's campaign never recovered.
"Right now the real goal (for Obama) is to make (Romney) look like a really rich guy ... who makes and hides money in ways that most people would find objectionable," Princeton University professor Julian Zelizer said.
"The goal is also to simply subvert the promise of something new, just as opponents of Obama in 2008 floated things from his background in Chicago to suggest that the candidate was not who you thought."
Gergen said that while Obama's strategy might be successful, it carried some risks for the president if he defeats Romney in the November 6 election.
"Politically all of these attacks may in the end work, but it's also clear that they are going to come at the expense of governing in a second term" by making it even tougher for Obama to work with Republicans, Gergen said.
"The attacker gets hurt, too."
(Additional reporting by Steve Holland; Editing by David Lindsey and David Brunnstrom)