The National Review attempts to make sense of the exit polls, surely a Quixotic task. If you ask voters what is the most important issue to them, then ask which candidate is most likely to solve the issue, you don't get answers that predict the election results.
I think the problem is that there's a big difference between the issues people say are important to them and the issues about which they support a specific solution. The economy and joblessness are on everyone's mind, but hardly anyone has a coherent notion of what either a President or a Congress can or should do about them. People may say that abortion or immigration are less important, but at least they have concrete ideas about how a politician should vote on those subjects. I suspect a lot of votes were cast as a result of gut feelings about issues that people claimed were low on their list of priorities.
That makes it hard to discern a real mandate. Not that the newly elected politicians will have any difficulty claiming one, but the 2016 mid-term elections could surprise everyone again if the politicians think the voters have their backs.