The problem that I have with this theory is that Rep. Duncan Hunter isn't the only "true" conservative running for President on the GOP side. There's still Rep. Tom Tancredo (already labeled by the mainstream media as a "one issue candidate" and a conservative gadfly, has many confrontations with other Republicans including the President on many issues besides illegal immigration, and has said things that bother many people), Newt Gingrich (despite all of his negative personal baggage and questions about whether he's fit for an executive political position), Rep. Ron Paul (who is more libertarian than conservative on many issues, considered a kook by many other conservatives, and many other conservatives still like him anyways), former Va. Governor Jim Gilmore (despite increasing taxes while Governor in Va. and his struggles with Va. Democrats and Va. RINO Republicans), John Cox (Who?), Michael Savage (thin-skinned and not much of a temperament whenever criticized on any issue), and possibly many others who may end up entering the GOP Presidential race later and maybe have a serious impact among conservative voters. Conservatives must also seriously understand and not ever rule out the possibility that someday, some "third political party/Independent candidate" for President may end up running that excites enough of the conservative voters base to the point that it ends up causing trouble for the eventual GOP candidate for President. All of these possibilities are there in '08 and/or beyond. Rep. Duncan Hunter seriously needs to be prepared to differentiate himself well against everyone that I have mentioned here.
Candidly, I really don't think DH has any reason to look over his shoulder at any of those candidates. They all have too much baggage of some kind. Hunter's only real negative is his lack of exposure, and he's gaining ground on that every day. It's pretyy early in the cycle.