Evangelical leaders didn't threaten so much as strongly urge McCain to put Mike Huckabee on the ticket in exchange for their support. So now's as good as any to take a quick look at Huckabee's case.

First, Huckabee is a top-notch politician. When he entered the presidential race, voters asked "Hucka-who?" But it took only a few debates, a few well-timed jokes, and Huckabee was winning them over with few resources and little other than great personal charm. For a while there the Club For Growth was alone in its denunciations of Huckabee's fiscal record. But the point is that voters like Huckabee. He speaks to them and would wear extremely well among the blue-collar voters McCain is aiming for in some of the battlegrounds. He doesn't bring much regional benefit to the ticket, but then that is an overestimated quality in a running mate.

The downside of Huckabee is from the Right. His fiscal record matched with some of his comments that verged too closely to nanny-statism scared many conservatives away from his candidacy. What they want to see in McCain's running mate is a little more "government is the problem" and a lot less "compassionate conservatism." Huckabee doesn't fit the bill in their eyes.

So in appealing to the social conservative set McCain would be alienating the fiscal conservative set (which, I should add, is already quite angry these days). Then there are the independent voters, who, if they have a beef with the Republican Party, it's not because it's too fiscally conservative; it's with their view that religious leaders are dominating the party. Huckabee wouldn't do much to counter that view.