No doubt, much of this is a rejection of "big-government" conservatism, which has dominated these last several years.
But as Daniel McCarthy notes, the only one current GOP candidate could truly claim to be an heir to the Goldwater philosophy:
No putatively conservative politician today—with the exception of Ron Paul —has the idealism of a Goldwater or brings together idealists like Bozell and Hess.Though they all would pay homage to his legacy, it is truly interesting that you'd be hard-pressed to find a modern-day GOP candidate who could be classified as a "Goldwaterite."
The Ron Paul phenomenon -- like it or not -- illustrates there is still a Goldwater constituency out there, starving for a leader. To use business terms, he's tapped into an under-served market.
Of course, it wasn't by design. Ron Paul is who he is, and the fact that he is filling this niche is pure happenstance. Still, I think it's interesting to note how the second most famous (arguably) conservative American politician of the 20th century has so few true heirs ...