Invite a public audience in any U.S. city to a debate called "Break Up the Big Banks" (with a flyer featuring a diagram of how one might carve up a fatted pig) and chances are the "for" side will have the thing sewn up before it begins.

But for extra insurance, the organizers of one such debate, held Oct. 16 in New York, lined up Simon Johnson and Richard Fisher to argue for the dismantling of the nation's largest institutions.

Their opponents, former J.P. Morgan investment banker Douglas Elliott, now a fellow at the Brookings Institution, and Paul Saltzman, president of The Clearing House Association, would face two of the most charismatic critics of the big money-center banks.

Johnson, the MIT professor and former International Monetary Fund economist, is well suited to the stage, with a British accent that lends extra authority to most everything he says.

The debonair Fisher, president of the Dallas Fed, has taken up the mantle as the Federal Reserve System's resident opponent of too-big-to-fail since Thomas Hoenig retired from the Kansas City Fed and moved over to the Federal Deposit Insurance Corp. With his slicked-back hair and ease at a microphone, Fisher calls to mind a younger Donald Rumsfeld.

The "for" side presented first and nearly turned its head start into a no contest. Explaining that the acronym SIFI refers to Systemically Important Financial Institutions, Fisher drew laughs with his alternate interpretation (Save If Failure Impending) and set off a roar observing that SIFI "sounds like a communicable disease—something that's transmitted by risky behavior indeed."

Next was Johnson, who, anticipating the "against" team's argument that big banks serve a specific purpose, deftly set up a straw man and knocked it down to devastating effect.

"[O]n the magic of big banks," he began, "have you felt it?" Adopting the cadence of an evangelist minister, he continued: "Have you seen around you, as the banks became bigger, great improvement in customer service? The reduction in fees? The better access to credit for all Americans?" The audience was clapping and laughing even before he reached his conclusion: "No. No, you have not."

If there was a way to top such showmanship, Elliott and Saltzman, two respected, but significantly lower profile subject matter experts, didn't find it.

But the audience, which filled two levels of the Kaufman Center auditorium on Manhattan's Upper West Side, listened patiently as Saltzman spoke of "improving the macro-prudential regulatory framework," and as Elliott tried to parse whether his opponents were actually calling for a Glass-Steagall-style breakup of big banks or simply advocating for a ceiling on asset size.

The debate, part of a live series hosted by Intelligence Squared U.S., drew financial industry types, school debate team captains, MBA students, interested neighborhood residents and business journalists, along with a mainly older and well-heeled crowd of Intelligence Squared subscription holders, who pay $400 to attend 10 debates on a surprisingly wide variety of topics. (A debate in September examined the U.S. drone program; one planned for December is on the value of veganism.) Each debate is streamed online and broadcast by more than 200 NPR stations around the country.

Audience members are polled both before and after the debate, and neither result is revealed until the end. The side that improves its score by the most percentage points wins. Spoiler alert: the "for" side on this night started with 37 percent of the vote, while "against" had 19 percent, leaving at least 44 percent of the audience in play, plus any partisans who could be persuaded to switch sides.

That nearly half the audience could be undecided about what has been such a fraught issue at the national level seemed unthinkable to me. But a woman I met outside the theater after the debate explained that some Intelligence Squared audience regulars, she among them, often vote "undecided" at the beginning just to make the final reveal more fun.

In round two, when the debaters addressed one another directly and took audience questions, the "against" team finally seemed to get traction. Saltzman said that between the living wills big banks have been forced to write and the wind-down measures outlined in the Dodd-Frank Act, even JPMorgan Chase in a hypothetical failure situation could be "successfully resolved under the current law and would not need to be bailed out."

There was an argument over how to interpret recent comments from the Bank of England's Andy Haldane, and a discussion of the Vickers Commission—that is, until Fisher suggested to his fellow debaters that they were losing their audience by prattling on about British regulators.

But Saltzman got the group back on point when he noted that much of the recent increase in industry concentration came from banks that acquired failing institutions at the behest of the federal government.

In the closing statements, Saltzman focused on the role big banks play in moving capital around the world for multinational clients, and invoked the savings and loan crisis as a reminder that the days of less concentration in banking weren't always so good. Fisher closed with an appeal to let taxpayers permanently off the hook for failures of banks that "were badly managed and ... encouraged basically to achieve a size and scale under the protection of the law."

Elliott used his final bit of time to argue that bankers weren't taking risks pre-crisis for the sake of maximizing whatever subsidies they might have been entitled to as TBTF institutions.

Last up was Johnson, who waxed eloquently, if a little off point, about President Teddy Roosevelt's courageous antitrust stand against the railroad monopolies in 1902. "Vote for democracy," he concluded. "Vote to break up the big banks."

And they did. Using keypads to register their votes, 49 percent of the audience indicated their solidarity with Johnson and Fisher, up 12 percentage points from the start of the evening.

But with backing of 39 percent of the audience, Elliott and Saltzman delivered an additional 20 percentage points to the "against" side, sealing the victory.

A few days later, Saltzman theorized what happened: "We have the technicalities on our side; they have the emotion on their side. But when our passion, when my passion, came out toward the end, I think we started to really convince people that everyone agrees on the same end point [of eliminating TBTF], we just have disagreements on how to best get there."

Satisfied with the win, he notes the outcome wasn't all good news for large banks. "Forty-nine percent of the people still voted to break up the big banks. It's not like I'm popping any champagne corks."

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