Although I think it's too early to be having this discussion,
John Hood has kicked things off over at the
Corner with what I believe to be a wrong-headed analysis of a
post-McCain field:
I think the big winner is Fred Thompson, with Mitt
Romney gaining a little, too and Rudy Giuliani losing (he has
always needed a large field to maintain his footing in a race where
he is the odd man out ideologically).
What Hood neglects is that McCain is currently pulling moderates
and independents, as well as national security voters, that may
otherwise vote for Giuliani (this would be especially significant
in New Hampshire), so I think Rudy actually stands to gain by an
early McCain exit. And in the one poll we have with McCain out of
the race, a Quinnipiac poll conducted in Florida, Ohio, and
Pennslyvania--Giuliani benefits the most. In Florida (which I bring
up because Hood singled it out), in the event of a McCain exit,
Rudy picks up 6 points, Thompson picks up 1 point, and Romney
remains the same.