Ron Paul, though I wouldn't exactly call him a "frontrunner".
Not sure where Tancredo stands on the WOT.
Nor would I so perhaps we should drop the phony straw hat arguments.
As an aside, I believe Tancredo supports the war. Obviously though, border security is his main issue. But that is wrapped in the larger issue of national security especially in respect to terrorism risks to America.
Brownback has backed way off supporting the WOT, as well.