Well Indiana is a Republican state, Ohio is lean-Republican, Pennsylvania is toss-up and Michigan is lean-Democrat, so as it is, it's a very balanced region. The South never had the kind of demographic variation that the Rust Belt has.
Michigan -- firmly Democratic. The state ordinarily votes "barely Democratic" in a close election (2000, 2004) and by a large margin in a Democratic blowout. It has proved essential if inadequate for Democratic Presidential victories since the 1960s. It hasn't voted for a GOP nominee in a close election since 1976... and then with a Favorite Son candidate.
Pennsylvania -- slightly-less Democratic than Michigan, but essentially the same pattern. In 2008 it went for Obama by 10% despite McCain pulling out the stops.
Ohio is slightly more Republican than the national average, and a genuine swing state. It has voted for the winner in every Presidential election since the 1970s.
Indiana is decidedly more Republican than the national average, voting for only three different Democratic nominees -- FDR and LBJ in blowouts, and Obama must have been a perfect fit for the state this time, almost a Favorite Son. Almost any other Democratic nominee loses Indiana.
The South is not so monolithic as it seems. Texas is very different from Arkansas, Arkansas is very different from Mississippi, Mississippi is very different from Florida, Florida is very different from Georgia... Obama won the Rust Belt except for West Virginia, and this time he split the South.
