There were clear winners and clear losers in Tuesday’s primaries—and, yes, there was a clear trend.

The winners were Democratic insurgents and Republican outsiders—and, intriguingly, labor unions and House Speaker Nancy Pelosi, D-California.

The losers were incumbents and insiders on both sides—including President Obama and Senate Majority Leader Mitch McConnell, R-Kentucky, and House Minority Leader John Boehner.

But the biggest loser of all was the notion that the real action this year is on the Republican side of the primary ballot.

In fact, it is all over the ballot. And that offers Democrats, especially progressive Democrats, both causes for concern and roadmaps for the rest of the election cycle. That’s where the trend that matters comes in: 2010 is shaping up as a year when populist anti-Washington sentiment (with a healthy layer of anti-bank and anti-big business messaging) plays well, no matter what party label is on a candidate. That’s something Democrats must understand if they hope to prevail come November.

Let’s begin by breaking the races down:

Pennslyvania Congressman Joe Sestak’s victory was the "headline" story of the night and it confirmed that Sestak was right when he calculated that Pennsylvania Democrats—who has have been voting against Arlen Specter since 1980, when he was the Republican senator they could never quite oust, would relish an opportunity to do the deed in a Democratic primary. Specter’s party switch was celebrated in Washington, and even in the Pennsylvania capitol of Harrisburg, but it remained a tough sell with Democratic voters at the grassroots. Sestak’s impressive 54-46 victory was indeed confirmed that, and his election night declaration that “this is what democracy looks like” was less a message for Specter than for the Democratic party establishment that—including President Obama—that tried to sell a five-term Republican senator (albeit a reasonably liberal one) to Democratic voters.

In Arkansas, Democratic Senator Blanche Lincoln, a centrist with conservative and corporate tendencies, also offended the base. She fared slightly better than Specter, gaining more votes that her chief challenger in the primary, Lieutenant Governor Bill Halter, who won essential support from organized labor and progressive groups. But Arkansas is a southern state where a runoff election is required if no candidate gets 50 percent of the vote. (The trend was running 33 percent for Lincoln, 42 percent for Halter.) So Lincoln and Halter will face one another in a June 8 contests that will be a bitter battle between national Democrats who are backing a lame incumbent—including President Obama and former President Clinton—and a populist insurgency that will have all the labor support it needs. Lincoln could still win but, at this point, she can only prevail by turning the race so ugly that she destroys her own chances in November.

Obama will have to keep backing Lincoln and that’s too bad because it pegs him as a president who is more about being a Democrat than about the “change” theme that elected him.

But don’t think that Obama was the only DC player who got on the wrong side of the voters.

In Kentucky, Rand Paul’s big Republican primary win was a blow to McConnell and the GOP party establishment—particularly former Vice President Dick Cheney, who despised the mildly anti-interventionist stances taken by the son of anti-war Congressman Ron Paul. McConnell put his credibility on the line when he backed insider Trey Grayson. Paul had the support of Tea Party activists, but there was a lot more going on with the man who celebrated his victory by quoting the rock band Rush’s libertarian lines about how “glittering prizes and endless compromises/shatter the illusion of integrity” and declared that he had no intention of making nice with the establishment. His November race was made easier by Democrats, who passed over populist Lieutenant Governor Dan Mongiardo in favor a cautious centrist Attorney General Jack Conway.

But the open Kentucky seat is currently held by a Republican, so a Paul win would not shift the partisan makeup of the Senate—just as a Sestak in Pennsylvania would hold a Democratic seat.

The real news from the partisan divide came from Pennsylvania’s 12^th congressional district, where voters filled the seat that went vacant with the death of Congressman John Murtha. This was supposed to be the big race for Republicans, who noted that the district voted for GOP presidential nominee John McCain in 2008 and has generally been trending to the right. Boehner threw everything he had, including money and (suntanned) face time into the fight. So, too, did Pelosi, who raised money and pulled all the strings she could for Democrat Mark Critz while, at the same time, giving him the space he needed to frame out 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 AFL-CIO alone organized efforts that made 33,000 phone calls, knocked on 16,000 doors and distributed 75,000 worksite flyers at 63 work sites in the district.

The result: A solid win for Critz.

Democratic Congressional Campaign Chair Rep. Chris Van Hollen was right when he said: "This was the only race in the country today where a Democrat faced off against a Republican and the results are clear.”

That said, Democrats are not in the clear.

This is a volatile year. Indeed, there is at least as much volatility on the Democratic side as the Republican side—despite all the Tea Party talk.

The primary season is helping Democrats in that it is allowing voters and grassroots groups to clear away weak and disappointing incumbents.

But Democrats ought not presume that they can run in November on a stay-the-course message. There is clear anger with Washington, as evidenced by the defeat of Specter, the forcing of Lincoln into a runoff and the nomination of Rand Paul. Democrats need to harness that anger—no easy task for a party that controls the White House, the Senate and the House—and to be flexible enough to allow candidates to run as real populists. Like Halter in Arkansas, Critz was loud and proud in his criticism of big banks and big businesses that let American workers and communities down by outsourcing jobs and factories.

Pelosi and the unions seem to be reading things right.

Obama and his White House team might want to take a few notes from the speaker and from labor leaders like AFL-CIO President Richard Trumka, who noted, correctly, that Pennsylvania winner Critz won as a populist whose “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.”