Different reasons:
Frank is an incumbent from the bluest of blue states.
Brown and Boxer were opposed by RINOs...self-proclaimed moderates with plenty of baggage.
Sharron Angle was despised and more vilified by the Republican part than the Democrats. When the party fails to provide support for a candidate in a state that is dominated by SEIU - what can you expect?
A single strategy won’t work everywhere, but what have we learned when we fail to run good conservative candidates? The real issue is, has the Republican party heard the message, and will they embrace the Tea Party in the future or will they take the party into obsolescence?
Meg Whitman was single-handedly brought down by one person—that vile Gloria Allred—CNN monitored the Twitters and they turned negative when the state found out she hired that illegal. geesh
You make another very good point. The Republican party did sabotage people like COD and to a big degree Angle.