J.D. Hamel made the case (prior to last night's debate):
Huntsman does a disservice to conservatism by branding himself as a moderate. He’s not a moderate. He believes in low taxes, free markets, balanced budgets, the importance of the family, and the wisdom of an active—but measured—American foreign policy. His career is a testament to the vitality of these ideas. He shouldn’t run from them.
Perry and Bachmann’s conservatism is defined by what it opposes: science, liberalism, and gays. Others insist that their conservatism is reflexively anti-government, but each supports the Federal Marriage Amendment, a proposal that would annul the marriages of gay couples—ripping apart new families, many of which count young children as members.
For a stark contrast between Huntsman and Perry on climate science, watch this clip.