The persistence of DC-centric nostalgia for a time that never existed is so weird. I don't even know what the word "polarization" means most of the time. We all know the history. Due to some historical quirks, the Democratic party especially but the Republican party as well were made up of weird geographic and ideological coalitions that didn't actually make any sense. This is only a good thing if you think political parties shouldn't actually stand for anything coherent nationally. Slowly everybody sorted themselves out a bit better and now, roughly speaking, we can say the Democrats are like this and the Republicans are like that.
I guess Mr. Cleaver didn't argue about politics very much, or something.