Frank Luntz has an interesting, if light, piece in today's LAT: Celebrity Gets Arnold Only So Far.
I think he overly discounts the name-recognition factor in this race. If there is indeed a long list of contenders, with only a plurality needed to win, then name recognition will be a larger issue than in a normal slog-through-the-primaries, duke-it-out in a two-party contest kind of election.
Plus, Arnie is far more popular and well-known than any of the celebs-cum-politicians than he mentions in the piece (both winners and losers).
Not to mention all of Arnie's free pub as a result of the recent release of T3.