There were clear winners and losers in the May 18 primaries—and, yes, a distinct trend. The winners were Democratic insurgents and Republican outsiders—and, intriguingly, unions and House Speaker Nancy Pelosi. The losers included President Obama and GOP Congressional leaders Mitch McConnell and John Boehner. In 2010, 
populist anti-Washington sentiment—with a healthy layer of anti-bank and anti–big business messaging—plays well, no matter which party label is on a candidate. That’s something Democrats must understand if they hope to prevail come November.

Pennsylvania Congressman Joe Sestak’s impressive victory in that state’s Senate primary was the headline story of the night. It was less a message for Arlen Specter, who had reached his sell-by date, than for a Democratic establishment that tried to sell a five-term GOP senator to Democratic voters. In Arkansas, Democratic Senator Blanche Lincoln, a centrist with conservative and corporate tendencies, was equally off-putting to base voters, who forced her into a runoff with primary challenger Bill Halter. The June 8 showdown will be a bitter battle between national Democrats backing a weakened incumbent and a populist insurgency powered by unions and the progressive netroots.

Don’t think that Obama was the only Washington player who got on the wrong side of the voters, however. In Kentucky, Rand Paul’s big Republican primary win was a blow to McConnell and the GOP establishment, who despise the mildly anti-interventionist stances taken by the son of antiwar Congressman Ron Paul. McConnell put his credibility on the line when he backed insider Trey Grayson. Paul, who had the support of Tea Party activists, promised in his victory speech that he won’t play nice with either party’s leadership.

So, what of the partisan divide? The news flash came from Pennsylvania’s 12th District, where voters filled the seat left vacant by the death of Congressman John Murtha. This was supposed to be the big race for Republicans, who noted that the district backed John McCain in 2008 and has been trending to the right. Boehner threw everything he had into the campaign of GOP contender Tim Burns. Pelosi did the same for Democrat Mark Critz. But the savvy Speaker was sure to give Critz the space he needed to frame a relatively populist message that made few accommodations with the Obama administration. Pelosi had a big ally in organized labor, which worked the district well and hit all the right notes when it came to fair trade and busting the banksters. The result: a solid win for Critz.

Democrats are not in the clear, however. Despite all the Tea Party talk, there is at least as much turbulence on the Democratic as the Republican side. Anger at Washington is widespread. Democrats have to harness that anger—no easy task for a party that controls the White House, the Senate and the House—and be flexible enough to allow candidates to run as real populists. Like Halter, Critz was loud and proud in his criticism of big banks and big businesses that let workers and communities down by outsourcing jobs and factories. Those themes must be central to the Democratic appeal this fall.

Obama and his White House team might want to take a few notes from Speaker Pelosi and from labor leaders like AFL-CIO president Richard Trumka, who noted correctly that Critz’s "victory demonstrates that when a candidate stands tall and proud on issues such as jobs and trade, the public will see through the lies and slime hurled by the right wing and big business."