The politics of torture remind me in many ways of the politics of crime. There's little room in the public discourse anymore for smart crime policy, because the politics of crime demand increasingly tough positions that are increasingly irrational. Sentencing policy, particularly on drug-related offenses, is perhaps the best illustrative example, but there are others, like California's long-running debate over its "three strikes" law. Rational policymaking gets squeezed out because legislators cannot afford politically to adopt any position which might make them look soft on crime even when such positions (like drug diversion programs, community policing, etc.) might make for better uses of state resources than tougher sentencing, tougher law enforcement, etc.
McCain is the exception to the rule. Will Huckabee follow soon?