TWO years ago Barack Obama picked Jon Huntsman, the governor of Utah, to serve as America’s ambassador to China. It was hailed as a clever stroke. Mr Huntsman is young and personable, a success in business and politics, fluent in Mandarin—and Republican. Not only could Mr Huntsman be ambassador to China, he could stay well away from politics until after 2012. Oops. This week Mr Huntsman announced his resignation. That means he will be free to explore a presidential run, and he has done nothi...