Joshua Green reports;

Initially, Warren appeared to follow the Hillary Clinton’s script in the Senate. But at a Banking Committee hearing on Wall Street oversight, it was clear that Warren’s convictions were not going to be muffled like Clinton’s. The hearing was a typically somnolent affair until her turn came to question the regulators testifying before the committee. Warren devoted the five minutes allotted her to the seemingly abstruse topic of banking settlements, such as the $1.9 billion fine the British megabank HSBC (HBC) agreed to pay the Justice Department after it was accused of laundering money for drug cartels (among other things).

In a short preamble, Warren admonished the regulators for not being more aggressive in taking big banks to trial, explaining how this harms the public interest. “If a party is unwilling to go to trial, either because they’re too timid or because they lack resources,” she said, “the consequence is they have a lot less leverage in all the settlements that occur.”

She continued: “We face some very special issues with big financial institutions. If they can break the law and drag in billions in profits, and then turn around and settle, paying out of those profits—they don’t have much incentive to follow the law. It’s also the case that every time there’s a settlement and not a trial, it means that we didn’t have those days and days and days of testimony about what those financial institutions have been up to.”

Warren was interrupted by applause from the gallery—something seldom heard at Banking Committee hearings. But her most effective line came afterward, in the question she posed to the regulators: “Can you identify when you last took [one of] the Wall Street banks to trial?”

Amazingly, none could. And the excuses proffered as to why they couldn’t reinforced Warren’s claim that banks that are “too big to fail” have also become “too big for trial.” “We have not had to do it as a practical matter to achieve our supervisory goals,” stammered Thomas J. Curry, the comptroller of the currency.

Eventually the Senate will have to legislate. And the next big fight may well be over whether to break up the big banks. An unlikely coalition of politicians and regulators on the left and right who favor this option has lately begun to take shape.