Historically speaking, there is a +4 D registered advantage. that being said, it is registered and not Likely voters. Also, the best guestimates say that there should be a +1 - +3 R this cycle. Which is still means little, other than those margins in swing states and there will be a rout this time, like Romney/Ryan 300+ EV rout.
I, personally ( just a numbers junkie) don't see 300EV but i do see a Romney/Ryan win.