The Tea Party movement is marginalizing itself with its actions in Delaware.
The movement has been enormously influential and effective because it has been clearly defined by fiscal and small-government issues that cut a wide swath through the electorate. In Delaware, the Tea Party is making a significant departure from the very set of core issues that has drawn in a broad spectrum of voters and new voters, and instead seems to be defining itself by issues such as abortion and gun rights.
This is why many Tea Party supporters will likely start to move away from association with the movement. (That, and those pesky personal issues and strange positions of O'Donnell's that should disqualify her as an endorsed candidate of any party or movement, regardless of her stated positions on primary issues.)
The Tea Party is still, undoubtedly, a net gain for the Republican Party, but there has been a price to pay. Christine O'Donnell's support by the Tea Party movement does not even remotely reflect the Tea Party support for candidates such as Scott Brown in Massachusetts. But like many effective movements, the Tea Party may be enjoying a brief but bright shelf life, meant to burn hot for a short time before flickering out — or at least settling into a lesser long-term role.
If the Tea Party tanks Mike Castle in Delaware and costs the Republicans the Senate, it will lose supporters in droves.