It's actually far more likely to be the other way around, due to the undue influence small, mid-Western States have on the electoral college - they're almost entirely heavily Republican.
I disagree.
The small states do have a disproportionate weight and are very staunchly Republican, yes. But they are still very small in the grand scheme of things. But lots of the states have very small numbers of electoral college votes (Montana, Wyoming and the Dakotas only have three apiece, for example). On the whole, the Drumpf safe seats are largely only giving him single figures of electors. The big exception is of course Texas (38).
By Contrast, Clinton's safe seats are generally larger. California has a whopping 55, Washington 12, Illinois 20, New York 29, Maryland 10, New Jersey 14... Again, not all of the Democratic states are large of course (Vermont has 3 votes) but you get the idea.
My point is, if you add up all the safe states (the states that are very likely to go to one candidate or the other) you'll end up with a big discrepancy. Clinton has 242 safe seats, and Drumpf has 180[1]. Either candidate will need 270 to win the election, so Clinton needs fewer swing states that Drumpf does. (Exact numbers may vary, but the point is Clinton has more safe votes than Drumpf).
This means that Clinton only needs to win one or two of the swing states in order to secure the presidency. On the other hand, Drumpf is left needing to win lots of the swing states (most notably Florida - many would say crucially) if he is to stand a chance. This means that Clinton needs fewer actual voters to swing than Drumpf will.
If you look at the actual polling, Clinton is ahead consistently, but the margin is so narrow that the real result may well be that Drumpf leading, and still within the margin of error.[2]
So I would argue that the probability of Drumpf winning the popular vote is much higher than the probability of him winning the electoral college. Conversely, the probability of Clinton winning the popular vote is lower than that of her winning the electoral college. This leads to the very real possibility that Drumpf could win the popular vote, and not the electoral college.
[1]http://www.independent.co.uk/voices/us-election-will-trump-clinton-win-electoral-college-swing-states-a7402351.html
[2]http://projects.fivethirtyeight.com/2016-election-forecast/?ex_cid=rrpromo