In some ways, Frank—an inelegant, blasphemous career politician whose very job depends on the approval of voters like the Bonds and their listeners—personifies everything Wall Street fears about Congress’ motives and capabilities.

Frank is famous for his biting wit and volcanic temper, for ridiculing arguments that he finds stupid, and for administering tongue-lashings to the industry executives in both public and private settings. A former Harvard Ph.D. candidate (he later earned a J.D. from the school), his only business experience comes from pumping gas at his father’s truck stop as a youth in Bayonne, New Jersey. His proclamation of a new era of regulation—and bold dismissal of more-cautious voices—has heightened already stratospheric anxieties on Wall Street, leading some to question whether Frank—or indeed, Congress—has the proper temperament and experience to rewrite the rules of the complex world of finance.

“I am apprehensive,” said Stephen Friedman, the former Goldman Sachs chairman who heads the New York Federal Reserve, in response to a question about Frank’s efforts during a panel discussion with bankers. “It is a frightening thought to me that Congress, without immense preparation, would try to take on that job and try to do it in a period where there would be thoughts of retribution and punishment and populism.”

Friedman was speaking at the Council on Foreign Relations in New York, in a wood-paneled hall packed with shell-shocked investment bankers and corporate lawyers on a grim morning in late November. The day before, the government had announced its second bailout of Citigroup, following a fretful week in which the bank’s stock fell below $5 a share and the giant institution appeared to teeter on the brink of bankruptcy. Still, William Donaldson, the co-founder and former C.E.O. of Donaldson Lufkin & Jenrette and a former S.E.C. chairman, warned the panel that hasty congressional action to impose new rules is “one of the big dangers now.”

Friedman, like other Wall Street elders, has suggested postponing changes until both markets and emotions have stabilized and appointing a “blue ribbon” panel (classic Washington-speak for punting on a tough issue) to study possible strategies. Frank says such an idea is “nonsense.” He has no sympathy for the hedge fund managers and other financial wizards who invented what he calls “magical money machines.”

As Frank explains to me, “They became intoxicated by their own technology.” Listening to him detailing his plans at a mile-a-minute pace, predicting the return of Roosevelt-style government, and heralding the inexorable ascendancy of liberal politics, intoxication is a word that naturally comes to mind, and one can’t help but recall other eras of inflated ambition. In business, they’re called bubbles; in politics, they’re called revolutions. When asked about the possibility that emboldened Democrats could go too far, Frank dismisses the historical precedents with typical self-assurance.

“That’s overlearning from history,” he snaps. “Who are the unreasonable people who are going to overreach?”

Frank, regarded even by many foes as having one of the sharpest minds in Congress, has never felt it was his role to dream up overarching theories. Rather, he chooses from others’ ideas, guided by his principles. At present, those principles are clear: He believes that the government should use its muscle to regulate the financial system. He believes that executive compensation at public companies should be capped. He believes that income inequality lies at the root of many of the country’s economic troubles and thinks taxes should therefore be used to redistribute wealth to the poor. He believes that derivatives markets and hedge fund activity should be brought into the open and subjected to rules and that the United States should sacrifice some measure of economic sovereignty to international regulatory institutions.

All of these ideas would have been controversial—some politically unthinkable—even a few months ago. Now, says Peter Wallison, a financial-policy fellow at the conservative American Enterprise Institute and a former adviser to Ronald Reagan, “he might actually get them done, and that worries me tremendously.”

The hotheaded right regards Frank as an easily ridiculed foil. He walks like a penguin and speaks in a distinctively sibilant, rapid-fire patois, casually tossing off references to economist Joseph Schumpeter, philosopher Georg Hegel, and comedian Henny Youngman. “I think the fact that I’m gay is part of the subtext,” Frank says. He came out of the closet in 1987, the first congressman to willingly do so, and since then, his name has been synonymous in certain circles with the brand of free-spending, free-loving liberalism that conservatives love to run against. Now his role in the economic crisis has further elevated his profile, making him prime fodder for the cable-television screamers.

In a confrontation that gained him instant immortality on YouTube, Frank found himself cast as the villain in a shouting match with Bill O’Reilly over the mortgage crisis. The Fox News host insisted that Frank, through his career-long push to expand housing options for lower-income families, was responsible for enlarging the portfolios of Fannie Mae and Freddie Mac and ultimately culpable for the meltdown of the two institutions. That is the Republican line of attack on Frank, and it enrages him, because when the G.O.P. ran Congress, nothing was done to rein in the companies’ ballooning balance sheets. Frank was the one who pushed through an oversight bill after the Democrats took control in 2007.

The truth is, for a long time, both parties prized homeownership above all else, but Frank was more skeptical than most, wondering aloud in public settings how all those subprime mortgages were ever going to be paid off. This legislative history is tangled, though, not easily reduced to a sound bite. O’Reilly had already devoted a segment of a previous show to one of Frank’s former partners, Herb Moses, an economist who once worked for Fannie Mae. (The two men broke up in 1998.) Now O’Reilly bellowed that Frank, unlike S.E.C. Chairman Christopher Cox, didn’t have the guts to admit fault in the widening economic mess.

FRANK: No, this is why your stupidity gets in the way of rational discussion. The fact is, it was 1994 that we passed a bill to tell the Fed to stop the subprime lending. We tried to get them to do it. The first time we were in power again, in 2007, we passed the bill to regulate Fannie Mae and Freddie Mac.
O'REILLY: Look, Congressman, you tried to put a happy face on this.
FRANK: I’m not putting a happy face on anything.
O'REILLY: At least Cox is man enough to say he screwed up. You’re not.
FRANK: Hey, Bill. This manliness stuff is very unbecoming from you.
O'REILLY: Cox is man enough to say he screwed up. You’re not.
FRANK: You think toughness is yelling and ranting and trying to bully. It’s not going to work with me.

Frank, who once said that in politics, “imitation isn’t the sincerest form of flattery—denunciation is,” later turned the showdown into a campaign ad with the opening line “The right wing is losing control.”