What issue, based on performance and voter response in most elections, led many to incorrectly predict a Democratic victory in 2016?

Question

Quizplus · Accepted Answer

Performance and voter response showcased a growing economy in the US which typically benefits the incumbent party, leading many to predict a Democratic victory. However, there were other factors such as voter turnout, the Electoral College system, and the appeal of the Republican candidate that ultimately resulted in a victory for the Republican party.

What Issue, Based on Performance and Voter Response in Most