Lein Shory weighs in today, in part regarding the Massachusetts race, but mostly dedicated to this point:
The Big Secret of politics is that there's no secret. The better candidate usually wins--especially in an open seat.
I'm not saying the better guy (or woman) wins. I'm not saying the better Congressman, or senator, or president wins. I'm saying the better candidate wins.
I don't mean to sell Lein's point short here, because candidates do matter (and even if they didn't, his graphic for last year's presidential election cracked me up).
You have to go back quite a ways to find a presidential race when the most appealing personality between the two nominees didn't wind up winning--although I'm not sure where you'd draw that line for 1976. Now there was a Battle of the Schlubs.
But. Events and facts on the ground matter too, and they can matter a great deal. I don't care how good a candidate Scott "No, not that Scott Brown" Brown was or how bad
The only thought experiment you have to perform if you doubt me is to ask yourself whether Coakley would have won in exactly the same electoral circumstances--meaning, a special election to replace Ted Kennedy--in 2007 or 2009. There's no doubt in my mind that she would have won in those years, and by a lot closer to the 30 points she led by a month ago than the five she lost by yesterday.
I think Lein is right in that massive ideological shifts are very rare in American politics. By my estimation we saw exactly two over the last century: 1932 and 1980. I suspect very strongly that Scott Brown is a senator today mostly because his opponent's party believed heart and soul that they'd added 2008 to that list. In that particular, yesterday and the events leading up to it indicate that they were sorely mistaken.