Jonathan Bernstein's answer:
Probably, Republican audiences don't want that kind of thing.
It's not that there are no solid, factual, arguments for the policies Republicans prefer. There certainly are! But a politician who tried to stick to those would be competing with the Glenn Becks of the party, and the Rush Limbaughs, and the Newt Gingriches, and the "facts" that those party leaders constantly trot out. Democrats, to be sure, have to compete with some fringe voices who have a dubious grasp of facts and policy, but for whatever reason those voices are kept on the fringe. That's just not the case for Republicans.
Also: their most recent former president was the worst in modern history. And both Bushes had a hard time arguing their way out of a paper bag. Let's face it: Clinton, whatever you think about his character, is one of a kind. Always was. I saw it in 1991 and, as a very green editor of TNR, realized almost instantly he was the next president:
"The magazine's support for Clinton was not only vigorous — "a journalistic soul kiss," says Shafer of City Paper — but early, extending to an attempt to create a self-fulfilling political prophecy by dubbing Clinton "the Anointed" on its Feb. 3, 1992, cover. "He was the most impressive politician I have ever seen," Sullivan says."
He reminded all of us of that last night. May Hitch forgive me.