The primary upsets in Pennsylvania, Arkansas, and Kentucky will be billed as signs of voter discontent with the Obama Administration and Congressional incumbents, as well as a dark forecast for the future of the Democratic Party. The Tea Party also scored a major hit with Rand Paul--whatever that means.

For all the excitement about Tea Party power, Rand Paul's Kentucky campaign is a wild card race carried by a movement filled with mixed and contradictory messages--some rather progressive (Paul's anti-imperialism) and some downright racist (We're all Arizonans!)

Look for a lot of uncomfortable mainstream Republicans, who stood by Mitch McConnell and Dick Cheney, and now have to show up at the unity rally on Saturday to make nice with the Tea Partiers they consider total wackos.

If Rand Paul won on sheer anti-establishment fever, Arlen Specter, the 80-year-old political switch-hitter, lost partly because he was too downright flexible--and too pragmatic-- for either party's base.

But most interestingly, in Arkansas, an insurgent campaign by the comparatively progressive Lieutenant Governor Bill Halter against middle-of-the-road Senator Blanche Lincoln seems to have prompted Lincoln to move left. Chamber of Commerce darling Lincoln recently introduced the toughest bank reform legislation Congress has seen since the Great Market Meltdown. By forcing banks to spin off their derivatives desks, the amendment to Chris Dodd's bank reform bill would leave the derivative-trading operations ineligible for a government bailout.

The Lincoln amendment undermines her opponent's efforts to tie her to Wall Street and the big banks. But while they are trying to sink the amendment, the banks are still betting on Lincoln. Securities and investment firms came in third among her top contributors, with $371,250 in contributions last cycle, according to the Center for Responsive Politics.

Whatever the reason for it, the amendment is a progressive breakthrough.

"In one fell swoop, Lincoln's measure will effectively protect taxpayers, downsize the behemoth banks, and end the federal guarantees behind big bank gambling. It's the strongest structural reform measure in the bill," writes Mary Bottari on BanksterUSA.

Bankster is urging people across the country to call their Senators' offices and urge them to vote for the Lincoln amendment.

That's important because, win, lose or go to a June 8 runoff after today's primary, Lincoln may find that her crusade is cut short by a very well organized opposition including lobbyists for Goldman Sachs and other derivatives daredevils and their favorite members of Congress, along with Ben Bernanke, Tim Geithner, and a host of other Wall Street friends in the Obama Administration.

Lincoln herself might not even expect it to pass.

But what the bank battle shows is that there can be some progressive pressure on conservative Democrats--even someone like Lincoln, who tied up health care reform and voted for the TARP before her conversion to populist crusader against Wall Street.

That's one way progressives can win in this primary season--no matter what the outcome.