The fate Griffith met Tuesday night — defeated handily, with main rival Mo Brooks winning more than 50 percent even with a third candidate on the ballot — mirrored what had already happened to Sen. Arlen Specter among Pennsylvania Democrats. Specter switched parties last April, at a moment that seemed as good for Democrats as Griffith’s leap seemed bad. Both candidates admitted part of the reason they jumped was to help themselves win reelection, but Specter was more nakedly calculating; he wasn’t ready, he said, to let Pennsylvania’s conservative GOP primary voters have the final say on whether he would continue to represent the state in the Senate. The conventional wisdom then was that Republican Pat Toomey would have rolled right over Specter in a GOP primary, but that Specter would probably be able to beat him in the general election.

Democrats in the state, though, weren’t as easily persuaded. Rep. Joe Sestak resisted establishment efforts to muscle him out of the race (including, yes, by dangling the prospect of some kind of job) and perservered even though longtime donors were advised by power players in the state that they shouldn’t give his campaign any money. And lo and behold, on a rainy primary day, Specter lost.

Of course, northern Alabama Republicans don’t have that much in common with union activists, liberals and the other die-hard Pennsylvania Democrats who turned out there last month. But what they both do seem to share is an unwillingness to go along with establishment marching orders without question. So far this year, that’s been the overwhelming trend — just ask Charlie Crist or Trey Grayson, chased out or defeated by their party base despite backing from national Republicans, or Sen. Bob Bennett, beaten soundly in Utah’s GOP convention before the primary even came along.

So Griffith’s loss Tuesday might be troubling for both parties. For Republicans, of course, it’s just the latest sign that the Tea Party folks the GOP has been depending on for energy in 2010 might spin farther and farther out of the party establishment’s sphere of influence. (And at some point, if your ground troops refuse to take any orders at all, are you really better off having them on your side?)

But for Democrats, who have been cheering Brooks on in hopes of avenging Griffith’s betrayal, there’s a hidden downside, too. Optimistic strategists in Washington keep saying that the mood in the country isn’t anti-Democratic, it’s anti-incumbent. Griffith’s defeat might prove them right — and they could still wind up having a brutal Nov. 2. After all, there are far more Democratic incumbents trying to hold onto their jobs this year than Republicans. If voters are really in a “throw the bums out” mood, which Tuesday’s result seems to add more evidence is the case, that math adds up to bad news for Democrats down the line.

The prime example of this is in Kentucky, a conservative state that never much cared for Barack Obama in 2008 and that has turned even more sharply against him, and against the national Democratic Party, since his presidency began. This, coupled with the feeble economy and the basic buyer’s remorse nature of midterm elections, should make the contest to replace retiring Sen. Jim Bunning a cakewalk for the GOP.

But it isn’t, because the GOP base, in a revolt against a party establishment that it believes has betrayed conservative principles, opted for Rand Paul in the May 18 primary, instead of Trey Grayson, the establishment’s choice. Within 24 hours, Paul was scrambling to prove to a national audience that he doesn’t actually oppose the Civil Rights Act of 1964. He’s now clammed up and shaken up his campaign staff, but Paul is an unseasoned candidate and a true believer. With more than five months to go until the election, further embarrassments seem inevitable.

Democrats, in other words, could end up stealing a Republican-held seat in a conservative state. The more controversial Paul becomes — the more he becomes the main issue in the Kentucky race, instead of Obama, Washington Democrats and the economy — the more conceivable it becomes that swing voters who are otherwise ready to vote against the Democrats will end up voting against Paul instead.

This, obviously, wouldn’t have been the case if Grayson were the GOP nominee. In a year like 2010, with the national climate so favorable to their party, there’s virtue for Republican candidates in being inconspicuous — something that the bland, cookie-cutter Grayson would have had no trouble pulling off. Paul? Not so much.

This same basic dynamic — the GOP base forcing the nomination of a deeply flawed candidate — could end up playing out in as many as nine Senate battleground venues, potentially saving Democrats from an electoral drubbing.

Take Nevada, where Majority Leader Harry Reid should, by most historical measures, be a goner. His polling numbers are poisonous, his long-term incumbency and D.C. insider status are severe drags, and his state’s independent voters seem eager to use the midterm to “send a message” to Obama.

But it’s looking more and more like the GOP will nominate Sharron Angle, a far-right former assemblywoman who has the ardent backing of the Tea Party movement. Like Paul in Kentucky, Angle herself could easily become an issue in the fall campaign. Making the race a referendum on the GOP candidate is Reid’s only hope. If Angle’s his foe, he’ll have a chance to do that.

Or there’s Florida, where the GOP base’s revolt against Charlie Crist has flushed the popular governor out of the party — and into an independent Senate bid that is attracting significant Democratic support. If Crist prevails, there’s now reason to believe he’ll vote with Democrats to organize the Senate next year. And in California, the flaky Carly Fiorina has marginalized another Tea Party favorite and surged ahead of moderate Tom Campbell in the GOP primary. If she wins the nomination, Fiorina will face Barbara Boxer, whose popularity is now ominously low — and who is surely grinning at the prospect of dodging Campbell.

The GOP base could also topple establishment favorites in primaries in Colorado, New Hampshire, Washington and Arizona — ideological triumphs that would severely complicate GOP prospects in fall races that would otherwise be very winnable. And the party base’s revolt in Pennsylvania last year, which prompted Arlen Specter to switch parties, has left the GOP with Pat Toomey, who faces an iffy fall campaign against Joe Sestak, who knocked off Specter in the primary.

Right now, Republicans need to pick up nine seats to draw even with the Democrats in the Senate (at which point Republicans could potentially win Joe Lieberman over) and ten to gain control of the chamber outright. The good news for them is that — especially with this week’s decision of Dino Rossi, an electable establishment favorite, to run for Patty Murray’s seat in Washington — there are (potentially) enough vulnerable Democratic incumbents to hit those numbers. And the national political climate only helps. The bad news is that just every time a Tea Party favorite wins a primary, it means the GOP won’t be fielding his strongest fall candidate — which could help Democrats claim seats they have no business winning in this environment.

This may be the biggest single difference between 2010 and the GOP revolution of 1994 — which many Republicans believe they can replicate this fall. In ’94, the party base was about as cranky and agitated as it now is; this is just how the right gets when it’s denied White House and congressional control. But that anger was largely trained on Bill Clinton and the Democratic Congress. The GOP base generally trusted — or at least was willing to work with — its party’s Washington establishment.

Not so in 2010. Now, the GOP base distrusts the establishment as much as it distrusts the Democrats. It’s a consequence of 1994. As Salon’s Gabriel Winant has noted, the election of a GOP Congress in ’94 (and then a GOP president in 2000) fundamentally altered the base’s expectations: It was time for the establishment to take all of its lip service to the base and put it into law.

But that, of course, didn’t happen. Newt Gingrich backed off his confrontation with Bill Clinton in 1995, George W. Bush campaigned on “compassionate conservatism,” and a Republican president and Congress spent the aughts expanding government and racking up massive debt.

No wonder that today, unlike 1994, the Republican base is unwilling to take the establishment at its word. The consequence is the proliferation of Tea party candidates — a proliferation that might just save the Democratic Congress come November.

Sure, it could simply be that Sestak, who was barely known to Pennsylvanians even on primary day, is enjoying the kind of bounce that often accompanies generally positive saturation news coverage. But it’s also easy to see that in opting for him over Specter, Democrats made a smart fall bet.

The very attributes that were supposed to make Sestak an easy mark — his lack of name recognition, experience and polish — are all working for him right now. He’s been in Congress since 2007, but he feels new to most Pennsylvanians. In the last week, he’s been introduced to them as a gutsy outsider who took on the Democratic establishment and knocked off a calculating, five-term incumbent. This image is a perfect match for the moment, with marginal voters frustrated with the ruling Democrats (part of the buyer’s remorse nature of most midterm elections) and furious with the Washington establishment in general. It’s almost impossible to conceive of Specter keeping these voters in the Democratic fold in November. But Sestak at least has the potential to.

Democrats in Arkansas may be on the verge of a similar switch-out, with Blanche Lincoln potentially facing defeat in a June 8 Democratic runoff. As with Specter, national Democrats have touted Lincoln as their best — and maybe only — hope of holding on to the seat. By conventional standards, this would probably be true: She’s succeeded in conservative Arkansas in part by defining herself in opposition to the national Democratic Party on key issues. But in 2010, the evidence suggests, Arkansans don’t see her as a “centrist.” They simply see her as a Washington insider — and a member of the party they’re already inclined to vote against.

Her Democratic foe, meanwhile, would ordinarily be seen as too liberal to win in the fall. Lt. Gov. Bill Halter has received substantial support from organized labor and from national liberal groups that are angry with Lincoln. Halter has avoided using the “l-word,” but he’s been running against Lincoln from the left. And yet, last Tuesday’s preliminary election returns — which showed Halter besting Lincoln in conservative pockets of the state — suggest Arkansans don’t see him as a lefty; they see him as an outsider. And that reputation will only grow if Halter manages to knock off Lincoln on June 8. Winning in the fall would still be tough, but Halter — like Sestak — clearly offers his party its best chance.

This same game can also work at the state level. Take New York, where state Attorney General Andrew Cuomo formally announced his gubernatorial candidacy over the weekend. Cuomo is only running because the incumbent, David Paterson, has been rendered politically toxic, in part because of his own blundering and in part because of voters’ general rage toward Albany. Cuomo, despite his pedigree, has managed to craft an outsider’s image, using the A.G.’s office to score enviable headlines while avoiding the taint that comes with dealing with the Legislature (or grappling with the state budget). Paterson would lose to just about any Republican this fall, but Cuomo — in polling released on Monday — leads each of the three prospective GOP candidates by more than 40 points.

Or there’s Colorado, where first-term Democratic Gov. Bill Ritter declined earlier this year to seek reelection. Like many other governors, he’d seen his numbers drop as the economy and his state’s budget woes worsened. A poll last week gave Ritter an approval rating of just 34 percent. And yet that same poll found the Democrats’ replacement candidate, Denver Mayor John Hickenlooper, notching a favorable score of 47 to 33 percent. In a general election trial heat, Hickenlooper and Republican Scott McInnis are tied at 44 percent — a far cry, no doubt, from where Ritter would be if he’d stuck it out.

In most races this fall, Democrats will be handicapped by their party affiliation. But by replacing embattled incumbents with “outsiders,” they can level the playing field in some crucial ways.

That said, this approach will probably be of limited use to the party this year. For one thing, the Democratic establishment (just like the GOP establishment) instinctively rallies around its incumbents. So efforts from the party’s leadership to nudge aside vulnerable incumbents have been (and will continue to be) limited. Democrats were able to gently persuade Chris Dodd to give up in Connecticut back in January, but that’s been the exception, not the rule.

Then there’s the calendar. Sestak’s electability advantage (and potentially Halter’s) has come as a genuine eye-opener to many Democrats. Only now are they recognizing how poisonous incumbency really is this year. You can argue that they should have seen it coming — it’s pretty clear, for instance, that Democrats would have had a better chance in last year’s New Jersey gubernatorial race if they’d replaced the doomed Jon Corzine with former acting Gov. Richard J. Codey — but as a practical matter, it’s now too late to organize credible primary challenges in most states and districts.

Still, if Democrats end up holding on to the Pennsylvania or Arkansas seats (or both), it almost certainly would be enough to save their Senate majority — rather impressive, considering the party establishment’s warning that throwing out incumbents would jeopardize both seats.

All the support the party establishment gave Specter, after all, was mostly just payback. Specter’s switch a year ago gave Democrats the 60th vote they needed to overcome Republican filibusters (after Al Franken was finally seated), and his support before that had helped pass the economic stimulus. By now, though, Specter isn’t the 60th vote anymore; Obama didn’t even care enough about whether he won or lost to risk a late campaign appearance on his behalf. Sestak — who stubbornly resisted entreaties to quit the race — hammered Specter constantly for cutting a deal for the White House help. But he also said he wants to be Obama’s “closest ally” if he makes it to the Senate. That doesn’t exactly sound like an anti-White House message.

There are signs of an enthusiasm gap: In January’s special Senate election in Massachusetts, voters came out in surprisingly high numbers. A total of 2,253,737 ballots were cast that day — the most in a non-presidential statewide contest in the Bay State since 1990 — as Republican Scott Brown defeated Martha Coakley.

In Pennsylvania’s Democratic primary on Tuesday, it was a different story, with turnout light across the state. In Philadelphia, for instance, it was on pace to hit around 170,000. Compare that to the city’s turnout in the 2002 gubernatorial primary (between ex-Mayor Ed Rendell and Bob Casey) when it was nearly 290,000. Statewide, the Specter-Sestak turnout tally was on course to be significantly lower than the ’02 total.

Sure, primaries and general elections are different species. But the contrast between Massachusetts and Pennsylvania speaks to the nature of midterm elections: The in-power party’s base tends to be disengaged, while the out-of-power party’s base is motivated (along with independents, who latch on to the out party as a protest vehicle). So it is that a hotly contested Senate primary did little to stir Pennsylvania’s Democratic electorate, while the opportunity to deliver a blow to Barack Obama and the Democratic Congress sent independents and Republicans (and even some conservative Democrats) flocking to the polls in Massachusetts.

Don’t fear the establishment: In Kentucky, the Senate Republican leader’s preferred candidate was destroyed in a Tea Party wave. In Arkansas, incumbent Sen. Blanche Lincoln struggled to win, much less get 50 percent of the vote, and a candidate no one took seriously at all wound up with 14 percent. In Pennsylvania, Arlen Specter’s whole campaign boiled down to a full-throated defense of incumbency and a collection of powerful endorsements.

It’s always easy to oversell the benefits of being in office and the usefulness of having other politicians weigh in on your behalf. But in 2010, it’s clear the establishment has very little clout, in either party, and incumbents need to start looking at their experience as a liability, not an asset.

Specter, in particular, ran the ultimate insider’s race. At his final press event Monday, he had boasted of his 20-plus votes for minimum wage laws. On Tuesday, he dropped by the Famous Deli for Philadelphia’s traditional Election Day lunch gathering of political operatives and union bosses — and sent a few dozen campaign volunteers to stand around outside, as if to show the power brokers he had a presence, instead of going to drag voters out to polling places in the rain. None of the pork he’d brought home over the years was enough to help him overcome a general Democratic revolt over his party switch; Sestak positioned himself as an outsider, hoping to tap the lingering anger at the system that have made the last two election cycles about change, and will likely power November’s voting, as well.

Sestak’s victory isn’t a liberal triumph: At first glance, the storyline out of Pennsylvania looks rock solid: Joe Sestak attacked Arlen Specter — former Republican — from the left and won, despite support from the Democratic establishment in Washington, Harrisburg and points between. But it’s not really that simple. Sestak and Specter barely disagreed on anything; Specter opposed the troop surge in Afghanistan, which Sestak opposed, and they both supported the healthcare reform bill. Late in the campaign, Sestak ripped Specter for attacking his support of an assault weapons ban, but he used that mostly to remind voters that Republicans had pulled out the same issue against Barack Obama in 2008.

Actually, independent polls showed — and Sestak campaign advisors told Salon — many conservative Democrats liked Sestak better than liberals did. Specter actually led Sestak in polls among liberal voters, and Sestak led Specter among conservatives. Sestak’s camp says his early TV ads, which focused on his biography — especially his career as a Navy admiral — meant their man was introduced to voters first as, basically, a military guy; that’s not the kind of thing that screams “liberal” to the electorate.

Essentially, Sestak won over progressive voters for two reasons: Many of them already liked him for his 2006 campaign against Republican Rep. Curt Weldon, and Arlen Specter spent most of his career as a Republican. Expect him to talk about “change,” and sound some populist, outsider themes during the fall campaign — but don’t look for him to become a new liberal hero.

A Republican House isn’t inevitable: The GOP’s confidence in its 2010 prospects has been soaring — and on paper, it’s made sense. Midterm elections always favor the out-of-power party, especially when unemployment is hovering near double digits. And there’s plenty of low-hanging fruit for the GOP to pursue this year — Republican-friendly districts that ended up in Democrats’ hands thanks to the collapse of the GOP in the 2006 and 2008 elections.

But Tuesday offered Republicans a sobering reality check, as the party failed to win a special election in the only House district in America that flipped from John Kerry in 2004 to John McCain in 2008. Yes, the GOP has a built-in excuse: Democratic turnout in Pennsylvania’s 12th District was aided by the state’s Democratic Senate primary. But that only counts for so much. The profile of the 12th — working-class, culturally conservative, never too keen on Obama in the first place — made it a perfect target for the GOP. But they ended up losing — by nearly 10 points. Republicans need to pick up 40 House seats to win back the chamber in November. That number looks a lot more imposing after Tuesday than it did before.