Jason Reifler, one of my colleagues at Duke (and an assistant professor at Loyola University Chicago in the fall), offers a telling analogy for who most resembles Bill Frist among past presidential contenders:

I think you missed the real reason behind Frists’s change of heart on
stem
cells. It’s not a break in his pandering parade, just the next
float. He
saw he was going to lose on stem cells because his position was
unpopular
and, if the Dems are right, stem cells will finally be a wedge issue
they
can use to their advantage.

In my view, Frist may be the new Steve Forbes. A guy who doesn’t
generate
a lot of warmth who is way overmatched in running for president and
is
constantly remaking himself to improve his numbers. Forbes caught on
in
’96 because 1) he had a simple message, 2) that was new (if you
forget
about Jerry Brown in ’92), and 3) ran against a pathetically weak
field.
And he still lost.

Update 8/2: Jason adds:

I realize only now that I left off part of the conclusion re: Frist.
He
lacks #1 and #2, a simple and novel message. He will likely have the
weak
field. Which only makes him that much more vulnerable because
somebody
with #1 and #2 could waltz right in.