Think of it this way. You want the Republican base (if you are a Republican) to support you, but if you like to kill babies it doesn't matter how Conservative you are, and if you like to suppress free speech, you don't get the Conservatives either.
The two top media supported candidates have been Giuliani and McCain and neither one of these guys can get the nomination.
McCain appeals to blue states, independents, vetrans, old person(a major voting block), etc.. he can win the general election. Romney is 5-10 points below McCain I think in potential for general election success.