What makes Ohio a bellwether?

[All Along The Watchtower]

Ohio is a regional crossroads in the US, with Southwestern Ohio ranging from rural small town Midwestern areas to the three major cities/growing metros of Cincinnati, Dayton, and Columbus (though Columbus is also close to Central Ohio), most of this region being heavily Republican (though parts of Cincinnati, Dayton, and Columbus are pretty Democratic) as an original "heartland" of the GOP; Northwestern Ohio, which is part of the "Rust Belt" and has centers of manufacturing like Toledo that are heavily unionized and vote Democratic (though there are, again, many pockets of Republicanism in this region as well); Northeastern Ohio, which has Cleveland, Akron, Youngstown, and other major "Rust Belt" areas that have undergone some population decline as well as revitalization and are heavily Dem; and Southeastern Ohio, which is close to West Virginia in geography as well as culture and whose heritage is conservative Democratic but has gotten more Republican as of late.

I think Ohio is a bellwether, partly because of coincidence and partly because it is essentially in the center of much of the "Old Yankee" United States (the Midwest and the Northeast) which, taken together, is the most populated region of the U.S. IIRC, Columbus is used by a lot of businesses doing research as some sort of a test market for products because of the population centers that surround it in a relatively short radius.