this election is a microcosm of the 2008 election.
personality...
brown is a centerfold model who brags about driving an american truck to far-right voters who care more about a flag pin on a shirt than a brain in the head. Brown's an anti-labor guy who isn't going to do much more than pump his fists yelling "America... Fvck yea!!" Coakley on the other hand, is a horrible candidate. lazy and shitty on many levels.
one major issue...
the economy. It was the war during the last election. Brown promises change. Nothing is gonna change if he wins. or, healthcare. brown wins, national healthcare fails, which benefits those in 49 states not called mass (but ensures Brown got crazy resourses).
mood of change....
broke people are voting against the status quo. GOOD!
So yeah... just like in 2008, you have a rock star against a stale candidate, the mood of change, and an issue where one person (coakley) is just on the wrong side of.