I believe I posted about this very question a while ago.
Indiana is, in my opinion, kind of strange in that it's a (mostly) red state surrounded by swing and blue states. My theory is that it's a state in the Midwest that historically, didn't take part in many of the trends that shaped the politics of the Midwest.
- It has no large cosmopolitan city like Illinois
- No large black population like in Michigan
- Not as many unionized manufacturing workers like in Ohio
- No large progressive Scandinavian immigrant population like in Wisconsin and Minnesota
Indiana is the best example today of what the Midwest might have looked like before movements like the great migration and the Rustbelt industrial boom shaped the region. It's a state where most people still claim German, protestant ancestry, full of small towns and farmers. Which, as someone said, was an original base of the Republican party.
yes, also you have a unique combination of Indiana being very lightly settled by New England Yankees compared to every other Midwestern state AND being significantly settled by 'Greater Appalachians'. The Yankee settlement band that stretches from northern PA and across OH's(northwestern reserve) narrows significantly across northern Indiana. I remember it having something to do with soil, but it might have been the Appalachians pushing north in southern Indiana -- that pushed the Midlanders North --- and the Yankees were boxed out- squeezed against lake Michigan.
So you have:
1) Midlanders who have probably been the longest lasting cultural base of the Republican party(with a brief exception of FDR realignment) ,
2) Greater Appalachians who tend to be somewhat Libertarian, and
3) a sliver of Midwestern Yankees who used to be Strong Republicans, but now produce mostly knee jerk leftists.
The early alignment would be Midlanders+Yankees vs. Appalachians
The current alignment would be Midlanders+ Appalachians vs. Yankees
The Republicans have always been able to form a majority coalition of the three groups is the bottom line answer.
