The unpopularity of the President and Obamacare were obviously very important factors here. But this shouldn't be ignored:
In precincts Romney won, voter turnout was 58% of what it was in November 2012.
In precincts Obama won, voter turnout was 48.5% of what it was in November 2012.
In other words, Sink had a huge turnout disadvantage.
Probably the most important post in this thread. It's not Alex Sink's fault these voters didn't turn out. They simply don't care about politics enough to vote in off years and midterms. To them a special election for the House of Representatives is about as important as a special election for a school board vacancy is for political junkies.
You're definitely right. Low turnout causes these problems. Most people just don't know what's going on in these special elections.
