Michigan Feels the Bern??

I was surprised to see my home state of Michigan go for Bernie Sanders in last night's primary. I didn't see that one coming and, apparently, neither did the pollsters. I was listening to NPR on the way home from work today and they spoke with someone from Nate Silver's polling service FiveThirtyEight about how the pollsters wrongly predicted that Clinton would win Michigan. The whole polling system sounds like a crap shoot these days. How many people actually still have landlines? And for those who don't, how many actually answers calls from pollsters that come via their cell phones? Not many, I suspect. I know I don't answer calls on my phone from numbers I don't recognize and I'm sure I'm not alone in doing that. So who are the pollsters actually polling?