The questions are posed by the WaPo’s Dan Balz.
The things to watch are outlined by Carrie Budoff Brown and Kenneth Vogel at Politico. Number two on their list:
Don’t be fooled by early results. The cities and suburbs usually report their returns first, which gives the candidate favored in those areas a quick — and sometimes fleeting — lead. The conservative-leaning small towns through the center of the state usually filter in much later in the evening.
… So Obama could show a lead in the early results, but it might be short-lived. If Clinton is ahead at the start, she may never lose it.
(That rule — cities and ‘burbs first, small towns second — might seem obvious, but in Missouri, at least in the 2006 mid-terms and the 2008 primary, the sequence tended to be just the opposite: Kansas City and St. Louis and their respective ‘burbs trickled in the latest, mitigating and sometimes reversing the small-town vote.)