While I think Cory's analysis is accurate (human beings adapt to strategies), I think that as one side builds up "wins", the winners become more complacent, and the losers become more motivated.
Sadly, this "regression to the mean" (okay, in politics, this "the mean" is jumping all the way to the other side) applies to all sides. It brought Trump in, and it will carry him off. Of course, a lot of damage can be done along the way (Brexit, etc.)
One other point - the US President is such a powerful symbol that it overshadows the much greater, but somewhat less visible, but quite possibly more meaningful power of the Senate, Congress, and State legislatures. I'm hoping that a Republican win the White House presages a strong push back against the total dominance of the Republicans in pretty much all walks of American political life.
I'm half convinced that if the only political position the Democrats held in the country was the presidency, that I and many of my cohort would be breathing a sigh of relief. Such is the power of symbols.