Jay Cost is usually pretty good. This piece is about the supposed bias against Trump in polling right now:
"The 2012 presidential polls were especially strange. The national polls had the race a
virtual dead heat for the final month (and the well-regarded Gallup poll
showed Mitt Romney ahead the whole month), but the state polls showed President Obama beating Romney fairly comfortably. The state polls turned out to be correct. Importantly, these errors have underestimated both
Democrats and Republicans over the last couple cycles. It is just not right to say that the polls have a pro-Democratic or pro-Republican tilt. They can be off by a few points in either direction. So—from our vantage point, here in late August—it is just as possible that the polls are understating Hillary Clinton's standing as they are Donald Trump's."
http://www.weeklystandard.com/are-the-polls-biased-against-trump/article/2003969
I think the weird 'state and national polls are different' thing is happening again. Read the other day that Hillary's average lead in national polls is around 5-6 points, but if you look at state polling, you'd expect her national lead to be about 8-9 points. And as everyone loves to say, we don't have a national election - we have 50 state elections.....