If done correctly, with no handicapping for dems, results of polls CAN be accurate. Problem is everyone these days has an agenda, everyone is so opinionated that they can’t see past their bias.
You can’t get accuracy with a country of 300 million people by calling 900 or even 10,000. The sample is far too small. Its a fact that anything including weather can affect turnout and nobody knows who will win. Its also a fact that Trump still has far more enthusiasm than Hillary, and Hillary will have abysmal turnout except in precincts with ballot box stuffing.