THE GOVERNOR OF the nation's largest state was reelected in a landslide in November, even though his Republican Party is a minority in California. He works with Democrats in a way that offers the rest of the country a model of much-needed bipartisanship. To kick off his second term, he has proposed the most ambitious healthcare and environmental reforms in the country, and he is also committed to a massive reconstruction of the state's infrastructure. Yet, oddly enough, Gov. Arnold Schwarzenegger is not on the list of potential presidential candidates in 2008. Why? Because the founders were worried in the...