There have been quite a few articles about the betting markets on the
next supreme court nomination.

The Washington Post noticed that there’s a difference between odds posted by bookies and the results of
markets. (The bookies were handicapped by having to make their
projects before the news was out about Sandra Day O’Connor retiring

But these markets suffer from the same problem as the market in which
Justice would retire first, and which Cardinal would be elevated to
Pope: a very small group has inside information, and everyone else is
just speculating. For the Supreme Court, it would be much more
relevant to have conditional markets in who, if nominated, would be
most likely to be confirmed, or to rule in certain directions. These
kinds of answers are more useful, both to the ultimate decision maker
(the President) and the various lobbyists, and also are the kinds of
questions that a much larger group of informed people could usefully
weigh in on.