After reviewing various difficulties with real-world polling,Cliff Zukin (professor of public policy and political science at the School for Planning and Public Policy and at the Eagleton Institute of Politics, Rutgers University) concludes:
Those paying close attention to the 2016 election should exercise caution as they read the polls. . . . We are less sure how to conduct good survey research now than we were four years ago, and much less than eight years ago. . . . Polls and pollsters are going to be less reliable. We may not even know when we’re off base. What this means for 2016 is anybody’s guess.