He has to fill the seat. If 45 democrats and 15 republicans will block his moderate nominee, and if 45 democrats and 7 republicans will block his conservative nominee, he'll have to send up another Ginsberg: who got all but 3 votes.
Looks like you've got this bunch figured out; that's exactly what they seem to want. They're doing a Ginrich: pulling defeat from the jaws of victory.