WAKE US WHEN BERNIE HAS A GOOD IDEA:

Breaking up the banks is one of those ideas that sound great in theory but less so in reality, a no-brainer until you run it through your brain. It's not that size doesn't matter at all, but the debate over size has been absurdly one-sided, ignoring the benefits of bigness, the potential costs of breakups, and what's already been done to address the too-big-to-fail problem. With Wall Street salaries and bonuses once again as exorbitant as they were before the recent financial crisis,  there will be huge pressure on 2016 candidates to prove their hostility to financial elites; on the Democratic side, Sanders and Martin O'Malley are already calling for bank breakups, so Hillary Clinton will surely be tempted to join them. But before financial disintegration becomes a populist litmus test, people ought to understand what it would mean.

For example: Did you know that the financial institutions at the heart of the 2008 crisis were not the very biggest banks? That the very biggest banks were actually indispensable to defusing the crisis? That the U.S. banking system is far less top-heavy than its foreign counterparts? It's possible to know those facts and still support the Too Big to Fail, Too Big to Exist Act, the chainsaw of a bill that Senator Sanders and Congressman Brad Sherman filed in early May. But they're important facts.

Before I explain, I should disclose that I helped former Treasury Secretary Timothy Geithner with his memoir about the recent crisis. But you can't blame Secretary Geithner for my views; I was writing favorably about the financial bailouts (which, by the way, ended up turning a profit for taxpayers) even before I met him. In any case, nobody wants the government to bail out irresponsible bankers. The question is how to structure and monitor the financial system to minimize the risk of the devastating crises that make bailouts inevitable.

Is splitting up financial behemoths the best way to minimize that risk? Some reformers think so. So do the small but well-organized "community banks" that tend to get their way on Capitol Hill. "This isn't a left-wing solution," Sherman told me. "Most banks endorse it!" They would, wouldn't they? There are about 6,800 banks in the U.S., and most of them would love to see the government take a hatchet to their largest competitors. Here are some points they rarely mention....

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