If you look at total numbers of votes cast for each candidate in each state, it looks like it was
1) in states like FL, big loss in number of blue voters.
2) in states like PA, uptick in red voter participation
Of these, the first seems more significant—Trump got fewer votes than Bush, Romney or McCain, so his vote total can’t have got up that much, while Clinton got 9 million votes fewer than Obama did. Clinton barely got more votes than Kerry did, and he lost.
Since the overall turnout was so low, I would suspect it was a turnout failure throwing off likely voter models, rather than people lying to pollsters. Though of course it could have been.