The pattern is a familiar one.
[IMGCAP(1)]Purist conservative challengers in GOP primaries start out as asterisks in early polls, but in the final week or two, they surge to victory, as national tea party groups pump money and energy into low-turnout primaries.
For the most part, these primary outcomes probably won't matter. Yes, Kentucky Secretary of State Trey Grayson would have had an easier time holding the state's Senate seat for Republicans in November than Rand Paul, but Paul is favored over state Democratic Attorney General Jack Conway, so the GOP primary upset shouldn't matter.
The same goes for Alaska, where little-known attorney Joe Miller shocked Sen. Lisa Murkowski in the Republican primary. Murkowski would have strolled to an easy re-election win, but with Democrats having their own weak Senate nominee, even Miller looks like a solid favorite.
In Colorado, former Lt. Gov. Jane Norton might well have been able to put together a broader general election coalition than Ken Buck, who defeated her in the GOP primary, but that isn't guaranteed. Buck is in a tossup race against appointed Democratic Sen. Michael Bennet, and he certainly has a chance in November. Maybe Norton would be better positioned for November, but it isn't clear yet.
And in Nevada, many have argued that Sharron Angle is a weak opponent against Senate Majority Leader Harry Reid (D), and she has made more than her share of mistakes. But the rest of the GOP field in Nevada wasn't anything to write home about. The smartest candidate in the Republican primary, and the Republican who would have added most in the Senate, John Chachas, spent most of his time living and working in New York City before becoming a candidate.
But Delaware is different.
Christine O'Donnell's victory over Rep. Mike Castle in the GOP primary effectively ends the party's chances of winning the Senate seat long held by Joseph Biden before his election as vice president.
For conservatives, that may be fine. As South Carolina Sen. Jim DeMint might say, better 30 dependable conservatives than 51 Republicans in name only. But Castle would have voted to organize the Senate for the GOP and would have voted most of the time with his party. Chris Coons, the New Castle County executive and the Democratic Senate nominee, will vote to have Democrats organize the Senate and will vote with his party virtually all of the time.
O'Donnell won the primary with 30,561 votes to 27,021 for Castle. But she is poorly positioned to appeal to general election voters, who are far more moderate than the true believers who supported her in the primary. And with many Republicans (including Castle) saying they will not support her, O'Donnell looks like a gift for the Democratic Senatorial Campaign Committee.
Indeed, one conservative Republican strategist who is no fan of Castle and could never be accused of supporting "establishment" candidates told me recently that O'Donnell is a "crackpot" who has no chance of winning the general election.
O'Donnell's conservatism is a problem for her in attracting support in a general election, but it isn't her biggest problem. Questions about her character are far more important and limit her appeal with the kinds of swing voters and soft Democrats that she would need to win.
Conservative Senate primary winners in Alaska, Kentucky, Nevada and Colorado don't face the same long odds O'Donnell does because those states are far more Republican and conservative to start with.
President Barack Obama drew 38 percent in Alaska, 41 percent in Kentucky, 55 percent in Nevada and 54 percent in Colorado. In Delaware, where Democrats have clear majorities in both chambers of the Legislature, he won with an overwhelming 62 percent.
Establishment Republicans in Kentucky, Colorado and Nevada may not be thrilled with their GOP nominees, but they'll still support them. That won't happen as easily in Delaware.
But Delaware does show the same thing that became apparent in Colorado, Alaska and Kentucky: Conservatives are energized.
A recent report from Gallup found that 63 percent of self-described conservatives said they had given "quite a lot" or "some" thought to the November elections — a far higher percentage than national adults (38 percent), non-Hispanic whites (42 percent), liberal Democrats (32 percent) or moderate and liberal Republicans (34 percent).
But in Delaware, winning conservatives isn't enough. It isn't close to enough. And that's why Christine O'Donnell and her tea party allies just won a battle but will lose the war.
Stuart Rothenberg is editor of the Rothenberg Political Report.