Remember when all polls used to be done by real polling companies that have existed for years/decades. What are these ing firms?
Strategic National is a consulting firm; they've been around for longer than 10 years, but I'm not sure how long they've done polling.
One thing that makes me worry about Michigan is the number of Trump yard signs I've seen in Wayne County--especially the blue collar suburbs (e.g., Lincoln Park, Wyandotte, Taylor, etc.) that have typically voted heavily Democratic. I'm not to the point of saying Trump will win Michigan, but I definitely think he has a chance here.
Really...yard signs? Is that you Peggy Noonan?
I've sometimes seen more Sanders stuff than Hillary stuff in towns Hillary won by ~50 points. It means nothing.
I'm not saying it's a definitive indicator, but it is something that should concern the Clinton camp. I'm not talking about just seeing Trump stuff in the cities overall... you have to ignore the yard signs placed in public places in order to get anything close to an accurate guess of support in the area; I'm talking about several Trump signs on streets where I've never seen a yard sign for a Republican candidate before.