The Economist investigates. Key conclusion:
Republicans’ disenchantment with their current presidential candidates is not an incidental characteristic of this crop of candidates. It’s a structural feature of a contemporary Republican Party whose pieces don’t hang together. Pro-Iraq-war neoconservative Republicans cannot actually live with Ron Paul Republicans. Wall Street-hating anti-bail-out Republicans cannot actually live with Wall Street-working bail-out-receiving Republicans. Evangelical-conservative Republicans cannot actually live with libertarian, socially liberal Republicans. Deficit-slashing Republicans cannot live with tax-slashing Republicans. Medicare-cutting Republicans cannot live with Medicare-defending Republicans. These factions have been glued together over the past three years by the intensity of their partisan hatred for Barack Obama, and all of the underlying resentments that antipathy masks.
For “all of the underlying resentments” read “racism.”