Like when?

Nate Silver at fivethirtyeight.com called 49 of 50 states correctly in 2008 and 2012. He looks at the averages of MANY polls and crunches the numbers. He's giving Trump a 33% chance of winning as of today.

Here is his state by state prediction:
http://projects.fivethirtyeight.com/2016-election-forecast/?ex_cid=rrpromo