The most important day in Jeb Bush's presidential campaign is Feb. 9. That's when New Hampshire residents vote and Bush's precarious campaign finally fizzles out or when he resurfaces as a leading candidate after months of teetering on the brink of irrelevance. Even more than Iowa's caucuses in just over a week, the Granite State primary should provide clarity to a contest that has defied prediction and long-held assumptions about presidential politics. "It's the first real inflection point," said Al Cardenas, a top Republican fundraiser and Bush supporter from Miami. "For some people, it's the definitive last stand. For some...