A presidential campaign exposes candidates' strengths and weaknesses. The strengths they're eager to tell you about. So let's look at the weaknesses.
Start with Rick Santorum, whose poll numbers in New Hampshire and South Carolina have been surging since (by last count) he lost the Iowa caucuses by the Chinese lucky number of 8 votes.
Santorum's weakness is that he can't resist concentrating on peripheral issues. The prime example is his leadership in 2005 in getting the Senate summoned into voting for a law preventing the removal of life support for Terri Schiavo.
Santorum's position was intellectually defensible (and shared by Democrats like Tom Harkin). But voters considered it weird to devote so much energy to a single unhappy legal case. I think this accounted more than anything else for Santorum's 59 percent to 41 percent defeat in Pennsylvania in 2006.
In New Hampshire, Santorum was unable Thursday to resist Boston radio talk show host Michael Graham's invitation to characterize himself as a "Jesus guy." Again, he had an intellectually coherent rationale.
And at an appearance in Windham that evening, he made it clear that he doesn't believe a candidate has to be a Christian -- a necessary concession in a nation whose Constitution bars any religious test for office.
But in discussing these issues, he needlessly gave credence to those who dismiss him as nothing more than a religious conservative when in fact he has a serious record on, and has been talking about, economic and foreign issues.
Jon Huntsman, even more dependent on a breakout in New Hampshire than Santorum, has a different weakness. His disdainful dismissal of other Republicans, even more than his service as Barack Obama's ambassador to China, has antagonized many conservatives.
At the same time it has attracted people who, like Huntsman supporters I've interviewed after his town halls, characterize him as the least bad alternative among the Republican candidates. And it's netted him the endorsement of liberal papers like the Concord Monitor and the Boston Globe.
Yet Huntsman's positions on economic issues are solidly conservative and have been praised by The Wall Street Journal. On education, he is a thoughtful backer of school choice. As governor of Utah, he took many smart conservative initiatives.
The tension between the anti-conservative aura he gives off and his genuinely conservative positions seems to have left Huntsman between two stools and struggling to achieve the solid third place finish in New Hampshire that might plausibly give him a ticket to other states.