Since we've got
this, it's pretty easy to make some maps factoring in turnout in a candidate's performance. I chose VAP rather than VEP because the difference in eligibility laws could bias the results.
I'll start with an evolution of the Democratic vote from 1980-2012 (interesting fact: in every election from 1984 to 2008, the dem % of VAP has systematically increased - 2012 was the first to reverse the trend, though even there Obama did better than any of his predecessors since
LBJ).
I used increments of 5%, so shades are worth half of their normal Atlas values (>20% is >10%, >70% is >35%, etc.).
1980:1984:1988:1992:1996:2000:2004:2008:2012: