Mitt Romney’s top strategist unleashed a strikingly personal attack on Barack Obama on Thursday, saying the president had reduced himself to “another politician who’s bullying an opponent.”

In an interview with The Daily Beast, Stuart Stevens responded to weeks of sustained criticism of Romney’s finances and business record by trying to turn the tables on the Democratic campaign. It was the latest sign of a more aggressive posture by a GOP team that has been decidedly on the defensive.

“Obama had something very special,” Stevens said. “He seemed above politics, and that made it difficult to attack him.

“They’ve completely squandered that in the last weeks. All the chest-pounding, the taunting, ‘no whining,’ ‘put on your big-boy pants’—he’d already become another politician in people’s eyes. And now he’s become another politician who’s bullying an opponent. I think that’s a big disappointment for people who like Barack Obama.”

Warming to the theme, Stevens said: “Once you’ve crossed that line, you can’t go back. I think they will look back on this period with great regret.”

It is a standard political tactic to question the motives of the other side or view with regret that the opposition has sunk so low. And the president’s people were not hesitant to punch back.

“Mitt Romney has put forward as his main credential his tenure as a corporate-buyout specialist at Bain Capital,” campaign spokesman Ben LaBolt said in an interview. “But he’s bristled at any discussion of that record because he profited off bankrupting companies and outsourcing jobs, applying an economic philosophy that the American people strongly disagree with.” He added that Obama has framed his campaign around the choice between two economic approaches, while Romney is “trying to both run on his Bain record and declare any discussion of it off limits.”

The Romney camp was emboldened by a New York Times/CBS poll that found its candidate a hair ahead of Obama, 47 to 46 percent, a statistical tie. Strategists noted that 14 percent of those surveyed said his experience at Bain made them more likely to vote for him, 23 percent said less likely, and 60 percent said it would make no difference.

Stevens also maintained that Romney has overcome a financial disadvantage—being outspent nearly 3 to 1 in eight swing states, according to a Washington Post report—in keeping the race neck and neck.

The prevailing view in Boston is that the media’s fixation on Romney’s wealth, Bain, and his tax returns is beside the point and that external events—mainly economic indicators—are virtually all that matter.

“This is a race about the economy, and what’s in the news doesn’t really affect how you feel about it,” Stevens told me. “People feel badly because they have less money to spend. Mitt Romney’s talking about the economy and the issues that matter, and the Obama campaign is trying to make people care about things they don’t care about. Neither campaign has the option of deciding what the dominant issue is. If you’re not speaking to that issue, you’re not really relevant in the race.”

Of course, this argument can be carried to an illogical extreme. Romney adviser Tara Wall, asked Thursday on MSNBC whether her candidate should have a more specific policy on the war in Afghanistan, said she was there to talk about the economy, adding, “These recent attacks on all these issues outside of what the issues are relevant to Mitt Romney are diverting away from what real Americans want to talk about.”

In the face of growing calls—including from some Republicans and conservative commentators—for Romney to release his tax returns, the campaign is doing its best to shut down that debate.

“The governor believes this is his personal financial situation and he’d already done what the law requires,” said campaign spokesman Kevin Madden. “His voice is the most prominent one in making the decision. Once you make the decision and execute it, you shouldn’t second-guess it.”

The point was underscored Thursday when Ann Romney told Good Morning America, “We’ve given all you people need to know and understand about our financial situation and how we live our life.”

One former Romney adviser says that’s exactly the right course. “In the big picture, this doesn’t matter,” says Alex Castellanos, a top strategist in Romney’s 2008 presidential campaign. “Voters don’t care about the candidate’s money; they care about their own money. It’s silly season.”

Castellanos fired back at the pundits who have been urging the Republican nominee to release more than a single year’s tax return, calling them “the pantywaist crowd.”

“This is why Bill Kristol and George Will don’t run campaigns,” he told me. “They’re great at what they do. They’re not great at running campaigns.”

Romney has been caught between two unpalatable alternatives. If he refuses to release more tax documents, the Obama campaign will spend the rest of the campaign slamming him as secretive and questioning what he’s trying to hide. But releasing additional thousands of pages opens up a can of political worms.

“Mitt Romney’s financial life is complex,” says Castellanos. “Obama’s attacks are simple. Giving them more to attack: not smart.”

He told me Romney should make this case: “I’m really successful and I’m being attacked for that success. If Obama doesn’t like it, too bad for him. He thinks success is something to be ashamed of. I think it’s very American.”

Each campaign always tries to claim the high ground, but the Romney folks believe Obama’s hope-and-change rhetoric in 2008 gives them an opening. Stevens said it was Obama who said in his acceptance speech that a campaign should be about grand issues.

“He’s trying to make it about the smallest of things when the campaign is about the largest of things,” Stevens said. “That hurts him.”