Were Southern Democrats stronger GE candidates?

[All Along The Watchtower]

I think this is more of a function of the one-party Democratic Solid South becoming politically competitive in the post-WWII decades, and also the nature of the South itself.

The South is a big region with a lot of people - ie. a lot of electoral votes, and historically its elected officials (in both parties, both white and black) have tended to form unified blocs to an unusual extent in American politics. Thus, Southerners have had an outsized influence within both parties (even now - a huge chunk of Hillary Clinton's base was in fact the Southern black vote).

Of course, that leads into the discussion about Super Tuesday's influence over the presidential nominations, etc.