Last week, a few dozen hedge fund and investment executives arrived at the Park Avenue home of Hamilton E. James, president of the private equity firm Blackstone. Each had paid $35,800 to spend two hours at a fund-raiser with President Obama, but the timing proved awkward: A few hours earlier, Mr. Obamas campaign had begun a blistering attack on Mitt Romneys career in private equity, the same business in which Mr. James has earned his many millions.

“Campaigns do what campaigns have to do, Mr. James later told friends. But not everyone was as forgiving. “People were incredulous, said one person who attended the dinner. “They could have waited a week.

Debates over how much to blame — and regulate — Wall Street have stoked tensions between Democrats and the financial industry ever since Mr. Obama took office amid a financial crisis. But now Mr. Obama is leveraging his bully pulpit and advertising dollars to argue that Mr. Romneys career as a successful financial executive exhibited values that are not those of a good president.

In doing so, he has not only drawn criticism from allies like Steven L. Rattner, the investor and former adviser on the auto industry, and Cory A. Booker, the mayor of Newark and a favorite of New Yorks hedge fund world. Mr. Obama may also be testing a bond first formed by Bill Clinton, who persuaded much of his partys elite that Democrats could be both populist and friendly to Wall Street.

“I think the consensus, such as it was, has badly eroded under the pressure of events, said William Galston, a former Clinton adviser who is now a senior fellow at the Brookings Institution. “The depth, the severity, and the length of the Great Recession have exacerbated strains within the country and within the Democratic coalition.

For some Democrats, the line Mr. Obama is trying to walk — between asserting that Mr. Romneys career at Bain Capital does not support his claim to be a job creator, and criticizing the private equity industry as a whole, between his acknowledgments of the vital role in the economy played by big investors and the scorching attack ads aired by his campaign — is a perilous one.

At stake are not only a political and policy relationship Democrats have nurtured over decades with the financial services industry, but the millions of dollars in campaign cash that have come with it. Already this year, securities and investment firms have given Republicans 59 percent of their donations, according to the Center for Responsive Politics, the partys highest share since the center began tabulating campaign money. Mr. Obama has raised millions of dollars on Wall Street, but far less than he did four years ago.

It is one of the most delicate topics within the party these days. Two Democrats with close ties to Wall Street, Senators Charles E. Schumer and Kirsten E. Gillibrand of New York, declined to comment on Wednesday. Other lobbyists, donors and industry executives declined to speak for the record, saying they did not want to highlight internal divisions and debates.

Peace, some Democrats noted, was easy to achieve during the boom years of the 1990s, when the Clinton administration favored Wall Street deregulation and financiers were lionized in the popular press.

The partys reigning economic orthodoxy then was Rubinomics, named for its prime author, the former Goldman Sachs chairman Robert Rubin, who felt that a credible attack on deficits would lower interest rates and spur economic growth. Even as recently as a few years ago, the alleged “bromance of Mr. Obama and Jamie Dimon, the president of JPMorganChase, was a running joke in Wall Street circles. Now Mr. Dimon calls himself “barely a Democrat.

Former Gov. Edward G. Rendell of Pennsylvania, a Democrat, said Wednesday that while he “didnt like the tone of the attacks on Bain, he thought the partys relationship with Wall Street had shifted with good reason.

“Wall Street screwed up the nations economy and the world economy, Mr. Rendell said. The White Houses approach to regulation was reasonable, he added. “What do they want us to do?

The gulf between Wall Street and the White House may well be more about noise than substance. Many bankers complain about tough language from the administration, with Mr. Obamas attacks on Bain merely the latest incarnation. And the administrations cold shoulder to the blue-ribbon deficit-reduction plan issued in 2010 by a bipartisan panel remains a sore point for many Wall Street executives who call themselves political moderates.

But some privately concede that Dodd-Frank and other regulations pushed by Mr. Obama have done little damage to their industry, and that the steps taken by the Bush and Obama administrations during the financial crisis starting four years ago averted what could have been a much worse outcome for them. (Even with a recent multibillion-dollar trading blunder, JPMorgan Chase is expected to earn $4 billion in the second quarter.)

And when it comes to personnel, Mr. Obamas White House is hardly hostile to Wall Street. Treasury Secretary Timothy F. Geithner took an early stand against proposals to nationalize ailing banks. The current director of the administrations National Economic Council, Gene B. Sperling, and his predecessor, Lawrence H. Summers, were both veterans of Mr. Clintons economics team — and both worked at investment firms before joining the Obama administration.

All three men who have served as Mr. Obamas White House chief of staff took private-sector detours through the financial industry: Rahm Emanuel (Wasserstein Perella), William M. Daley (JPMorgan Chase), and Jacob Lew (Citigroup). Two private equity executives, Richard D. Parsons, a senior adviser to Providence Equity Partners who retired last month as chairman of Citigroup, and Mark T. Gallogly, a founder of Centerbridge Partners and a top Obama donor, sit on the Presidents Council on Jobs and Competitiveness.

Senator Richard J. Durbin of Illinois, the second-highest-ranking Democrat in the Senate, said he had not heard of any Wall Street donors turning their backs on his party. But if it happened, Mr. Durbin said, Democrats should stick to their principles.

“Perhaps some will conclude that they cannot support any Democrats now, Mr. Durbin said. “I have heard Jamie Dimon talk about how hes barely a Democrat and he hates regulations — but look at what just happened. If we walk away from that because we have to pick up some campaign donations, wed be totally abdicating our responsibilities.