Capital University law prof, former FEC Commissioner, and Romney supporter Brad Smith has this to say about why so few conservative law professors have jumped on the McCain bandwagon:

I think that conservative law professors, who as I say, probably care more about the issue of judges and are on average in a better position to consider the candidates on this particular issue than are most other conservative activists, don't like what they see in McCain. Some of it is the problem of McCain-Feingold. McCain is likely to make support for McCain-Feingold - an issue he has said is "of transcendent importance" to him - a litmus test for judges. It is very hard, however, to find judicial candidates who think McCain-Feingold is constitutional yet who are also are anti-Roe v. Wade and generally respectful of the Constitution. For anyone with a coherent judicial philosophy of federalism and limited government, the two just don't go together. When McCain says he wants to appoint justices like Thomas and Scalia, we must consider that Thomas and Scalia would overrule all of McCain-Feingold, indeed all pre-existing campaign finance law except perhaps some disclosure. It is almost impossible to believe that Senator McCain would appoint Thomas or Scalia to the bench, let alone the Supreme Court.

Of course, there was a time when conservatives were significantly less sympathetic to a broad interpretation of the the First Amendment than were liberals. Perhaps President McCain will regress conservatives to the historical mean.