Given that the national union leadership is pretty much out for sHrILLARY, were I a union member receiving a random phone call there would be no way on God’s green erf I would tell them I was a Trump supporter. Who knows if the union was counting heads via a faux poll and I might never work again.
I think you have put your finger on it: These days more and more people are realizing that the pollsters are, for a host of reasons, NOT benign, and so the ones polled are not as openly cooperating as they have in the past.