I don't quit.

That was President Barack Obama's message to America in this week's State of the Union Address, as he sought to reassure voters that he hadn't forgotten—and wasn't going to give up—on his plans to change America.

Wall Street, however, was one part of his constituency that didn't need any reminder that the president remains determined to shake things up. After all, the speech came less than a week after another, shorter one, in which Obama introduced the world to what has been dubbed the "Volcker Plan." A package of proposals to split off the riskiest and most self-dealing parts of Wall Street—proprietary trading, in-house hedge funds, and private equity operations—from the parts of it that serve clients, the plan would, the president claimed, ensure that "never again" would the surviving banks help bring the financial system to the edge of the precipice.

Yup, the honeymoon is over.

Just as the president served notice on Republicans in Congress that he's going to demand a degree of cooperation from them—now that they have that crucial extra Senate seat that permits them to filibuster to their hearts' content—he's making it very clear to Wall Street that he's going to play the populist card from here on out when it comes to regulating their businesses. "If these firms can afford to hand out big bonuses again," he thundered to Americans, "they can afford a moderate fee to pay back the taxpayers who rescued them in their time of need." (The pronouncement got a hearty round of applause.)

When Obama was first elected, Wall Street had reason to be guardedly optimistic. First of all, the new president didn't abandon the essentials of the bailout program cobbled together in the waning days of the Bush regime. While he and members of his administration might thunder about the greed of Wall Street (remember the scathing remarks about its "culture of narrow self-interest"?) and propose pay caps, most of those policies seemed to wither on the vine.

Yes, Wall Street was still cautious—Lloyd Blankfein cautioned Goldman Sachs bankers to avoid any conspicuous consumption with their earnings—but was beginning to relax as profits revived last spring. Just as the French aristocrats and haute bourgeoisie figured they could work with the quasi-parliamentary democracy of the Third Estate in the early days of the French Revolution, Wall Street seemed to have decided that it could live with the Obama administration's mixture of tough rhetoric and de facto benign neglect. A consumer financial protection agency? Really, not that big a challenge to their core business. Less leverage under Fed supervision? Sure, they could live with that, at least for the time being.

But even as the last of the big banks were paying off their TARP loans, it suddenly became clear that while they had believed they were negotiating with people who understood them—a coterie of democratic reformists, like Lafayette and Mirabeau—they in fact were confronting an altogether more terrifying prospect: a latter-day Robespierre.

The original Robespierre believed fervently that the only way to preserve the fledgling French Republic was to preserve public virtue—by force, if necessary. "To punish the oppressors of humanity is clemency," he reasoned. "To forgive them is barbarity." And it seems as if the 21st century president of the United States shares that credo with his 18th century French predecessor, at least when it comes to Wall Street.