During the live-blog of Tuesday’s night debate, I observed that Hillary Clinton was probably winning the battle to redefine herself as “tough on Wall Street” by sheer assertions about her new banking plan, along with the failure of O’Malley and Sanders to explain why restoring Glass-Steagall (not a kitchen-table sort of topic) was such a big and indispensable deal.

But now here’s a vastly better authority than I am on the subject:

Hillary Clinton and Bernie Sanders had an argument about financial regulation during Tuesday’s debate — but it wasn’t about whether to crack down on banks. Instead, it was about whose plan was tougher. The contrast with Republicans like Jeb Bush or Marco Rubio, who have pledged to reverse even the moderate financial reforms enacted in 2010, couldn’t be stronger.

For what it’s worth, Mrs. Clinton had the better case. Mr. Sanders has been focused on restoring Glass-Steagall, the rule that separated deposit-taking banks from riskier wheeling and dealing. And repealing Glass-Steagall was indeed a mistake. But it’s not what caused the financial crisis, which arose instead from “shadow banks” like Lehman Brothers, which don’t take deposits but can nonetheless wreak havoc when they fail. Mrs. Clinton has laid out a plan to rein in shadow banks; so far, Mr. Sanders hasn’t.

“For what it’s worth” is quite a bit, because it’s from Paul Krugman. But won’t HRC fall back into her sinful ways the minute she wins the Democratic nomination? Probably not, says Krugman, because Wall Street just isn’t a Democratic constituency, even as a hedge, any more:

[I]f Wall Street’s attitude and its political giving are any indication, financiers themselves believe that any Democrat, Mrs. Clinton very much included, would be serious about policing their industry’s excesses. And that’s why they’re doing all they can to elect a Republican.

This attitude has developed into a powerful partisan bent on Wall Street since 2008:

By any normal standard, President Obama has been remarkably restrained in his criticisms of Wall Street. But with great wealth comes great pettiness: These are men accustomed to obsequious deference, and they took even mild comments about bad behavior by some of their number as an unforgivable insult.

Furthermore, while the Dodd-Frank financial regulation bill enacted in 2010 was much weaker than many reformers had wanted, it was far from toothless. The Consumer Financial Protection Bureau has proved highly effective, and the “too big to fail” subsidy appears to have mostly gone away. That is, big financial institutions that would probably be bailed out in a future crisis no longer seem to be able to raise funds more cheaply than smaller players, perhaps because “systemically important” institutions are now subject to extra regulations, including the requirement that they set aside more capital.

While this is good news for taxpayers and the economy, financiers bitterly resent any constraints on their ability to gamble with other people’s money, and they are voting with their checkbooks. Financial tycoons loom large among the tiny group of wealthy families that is dominating campaign finance this election cycle — a group that overwhelmingly supports Republicans. Hedge funds used to give the majority of their contributions to Democrats, but since 2010 they have flipped almost totally to the G.O.P.

You can attack her husband’s economic policies all day long, and excoriate Hillary Clinton’s positions when she was in the Senate where, as she candidly admitted Tuesday night, Wall Street was literally a New York constituent. But if you’re going to look cynically at the connections between Wall Street and certain kinds of Democrats, then you need to acknowledge those connections have significantly eroded. Or so says Krugman, who’s about as popular on Wall Street these days as Bernie Sanders.

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Ed Kilgore is a political columnist for New York and managing editor at the Democratic Strategist website. He was a contributing writer at the Washington Monthly from January 2012 until November 2015, and was the principal contributor to the Political Animal blog.