Three senators would definitely vote against that candidate: Cheffee, Snowe, Collins. Right there you have gone from 55-45 to 52-48. Now subtract the support of the cowards, Voinovich and DeWine. That brings you to 50-50.
At that point, all you would need is to lose the vote of Hagel, McCain, or Spector, and the candidate would not be confirmed.
Name those democrats who might vote "Yes." I am damn sure it isn't going to be Bayh, who is my senator.