Fred caught the Clinton spin and smear machine off guard. Doubtless, Car-vile and the War Room lads have reams of material on Giuliani and Romney (that they’re holding for the general election), but they haven’t had a chance to prepare a proper dossier on Fred. That explains the weakness of the attacks on the Former Senator, and the terror he seems to instill in the Drive-by Media.
That's really all it amounts to. What can they nail Fred with? Maturity? Equanimity? Virility? Wolves do not select the alpha male to attack, and they don't relish the idea of fighting him.
Their own anticipated candidate is a weak one, and they don't want the debate to be about her shortcomings.
After all is said and done, a presidential election is decided on one word: presidential. Fred is.