A lot of people say that Indiana is conservative/Republican because of its rural-ness, but actually many states are more rural and less Republican than Indiana (including Midwestern states such as Minn., Iowa, and Wisc.)
Perhaps Indiana is Republican because it has relatively few ethnic whites, Hispanics, or Asians.
Actually there are a ton of Hispanics in Indianapolis and the city is becoming Little Mexico. A street I frequented as a kid turned from vintage 50s style to the ugly and beaten down Hispanic shops like we have here in Arizona in the ghetto parts of town. And I wouldnt assume Asians are very democratic, it depends on where they are at. The vote swings either way with Asians. You are right about ethnic whites, unless you count the Amish, who vote republican.
How Latino is Marion County now?
About 11%
White (Non Hispanic) 54%
Black 29 %
Hispanic 11%
Asian 4%
I'm guessing that that's higher in select parts of the city.