He knows he is being sent to fight a losing fight, to the further harm of his party as obstructionists with no ideas. The hardcore left (NOW, MorOn...er, MoveOn, NARAL etc.) are going nuclear with this pick. Thanks to the 'net, they've got hundreds of thousands of misguided souls slamming all of the 'Rats to fight this pick to the death. I'd hate to be a staffer for a 'Rat senator right now....
"...to the death..." I like the sound of that. It might well end up being the death rattle of the 'Rat party in its current incarnation.