Another way of looking at this is to take some of the most successful Presidential Campaigns of all time, and compare them to how states flipped.
Ohio : Toss up, some polls have Hillary leading, others Trump leads. (No Republican has ever won the Presidency without Ohio) (Obama carried Ohio in 2012) (Obama also carried Ohio in 2008).
-Ohio has not gone Red since 2004 Bush vs Kerry.
Michigan, Wisconsin, Minnesota - Of these three, Only Michigan has broken rank with Democrats since 1988. Michigan went for Bush Senior.
Currently Clinton holds a +10 advantage in Michigan, putting it outside the realm of polling data discrepency.
North Carolina - Went to Obama in 2008, and then went to Romney in 2012. Currently Hillary holds a +4 margin in North Carolina.
Virginia - Went to Obama in 2008, 2012, but before Obama, Virginia had not gone Blue in multiple decades. If Trump were to win, Virginia would in theory be a great place to put resources. Clinton holds a +3 point lead in Virginia however.
New Mexico- has only gone Red once since 1988. George W. Bush was able to win New Mexico in 2004. Most recent polling data has Clinton ahead in New Mexico by +13. This is no longer within the margin of polling data discrepancy.
Nevada - historically Nevada always votes for the winner. Nevada went for GW Bush both times in 2000-2004, went for Clinton both times in 1992-96, and went for Obama both times also. If Trump has a chance to win, it will be in Nevada. The next debate is in Nevada also. Clinton currently leads by +3 in Nevada.