So marion is 3 parts?
Urban minority inner middle north. Rich white parts in the north along with yuppies and south is WWC?
Bingo.
And if you really want an illustration in stark relief, compare the precinct map of 2008 Presidential vs 2016 Presidential. Those solid Hillary precincts were solid McCain. Meanwhile, a lot of slight Obama precincts went heavily for Trump.
I don't have figures for population change, but it can't possibly be the results of changing demographics. The big growth is by and large happening in the "donut counties." This is the result of voters flipping party affiliation. Conservative Democrats (the Bayh family) are gone. "Business" Republicans (the Dick Lugar, Greg Ballard) are endangered.