The Why:

Both Giuliani and Robertson share an apocalyptic worldview about the clash with [radical] Islam; for Robertson, it is religious and based in biblical prophecy. For Giuliani, it is secular -- but given his 9/11 experiences, just as personal.

Evangelical Christians cite the war on terror as their chief policy concern, and it is not that surprising that Giuliani, who is more identified with an aggressive prosecution of that war than any other candidate, is doing well among evangelicals. It's not that they ignore his views on social issues; it's that they see the war on terror like he does: black-and-white, good-versus-evil, a struggle for the soul of civilization.

Robertson's legacy is greater than his influence these days, but remember: in 2000, it was John McCain's attacks against Robertson (and Jerry Falwell) that arguably doomed his campaign after South Carolina. Social conservatives may be warier of Robertson than they once were, but he is a pillar of their movement and is greatly responsible for legitimating their political activism.