It shouldn't be surprising that Democrats lost a seat Obama barely won despite his vaunted and massive turnout machine in a presidential year. As I've written time and time again, Democrats suffer from poor non-presidential year turnout among its most important base voter groups.
While there are no exit polls, there are clear signs of that base Democratic voter dropoff. Like this:
Given the GOP's effective 2010 gerrymandering, there aren't a lot of opportunities for Democrats to make gains, and this is a rare Obama district held by a GOPer. I'd be willing to bet that November turnout would make this a tighter race, and 2016 will be a whole other beast. The GOP is holding this district on borrowed time.
But given our anemic base turnout, Democratic candidates need to do a better job motivating them to vote. And in this case, I don't blame our base voters. When Democrats like Alex Sink run on austerity, cutting Social Security and bringing back the Simpson-Bowles Catfood Commission, well, no one is inspired. That has to be part of any effective base-mobilization strategy. Maybe promising to be a dick wins over some independent support (Sink did win the early vote despite the outsized GOP numbers), but that's as relevant as Mitt Romney winning independents by double digits in 2012. Democrats win by getting Democrats to the polls. There are more of us than there are of them. Period.
Still, last night wasn't a disaster: