What's wrong is that we have two different electorates that are increasingly different from each other and the way our system is set up means that we have wild, embarrassing swings from pathetic ~40% turnout rates. The end result is a wildly unstable and schizophrenic government that doesn't represent the broader population, exacerbated by other issues such as voting rights restrictions, gerrymandering, the nature of the Senate, etc.
Is it guaranteed that the coalition of voters that propelled Obama to victory twice will come out in full force again in two years, though?
I followed this election exclusively on CNN and maybe they will be proven wrong, but at some point both Republican and Democratic pundits said it's conceivable that a sizable chunk of the voters that made the difference in 2008 and 2012 (i.e. young voters, minorities, women) are mainly loyal to Obama and not to the Democratic Party. The conclusion was that with someone else leading the Democratic ticket in 2016, many of them simply might not show up to vote.