I can't begin to predict how a U.S. Senator will act, except Ted kennedy. But if Alito were to get a Dem vote out of Committee ( though not convinced it'll happen), imo, Kohl would be a likely choice. Wisconsin was close last presidential election. That is why Feingold and Kohl voted for Roberts. Feingold is running for President so unlikely he'll vote for Alito despite the closeness of his state. Voting for Roberts to replace rehnquist is forgiveable. The hard left is unlikely to forgive Alito for O'Connor. Kohl isn't running for President, he needs to only consider how voting against Alito could come back to haunt him if his state continue to drift right.
A democrat does NOT understand FEDERALISM!