There are few certainties in American politics. But you can write it down: If Hillary Clinton wants to be the next nominee of the Democratic Party to be president, the job is hers. Joe Biden, Andrew Cuomo, Mark Warner, Martin O'Malley and the others in the long list of commander-in-chief wannabes will go about their day jobs for the next couple years, but at the back of their minds will be only one question: Will she or won't she?