Those who say "we may lose control of the Senate if we lose that seat"-remember Specter. The GOP backed him; and he alone was enough to give us Obama Care after he pulled a Judas on us.
Better the devil you know...
In the event that O’Donnell loses, the Castles of the GOP win. FReepers are claiming victory against RINOs, but that war cannot be won until Tea Party candidates are victorious in the general. Motivated activists can always win low-turnout primaries.