It's not quite that simple, because the American political parties are coalitions. For the middle of the 20th century the Democratic Party was an odd coalition

It's not quite that simple, because the American political parties are coalitions. For the middle of the 20th century the Democratic Party was an odd coalition that joined organized labor and northern populists with Dixiecrats (conservative southern Democrats opposed to civil rights), while the Republicans represented both northern big business (the Rockefeller faction) and more libertarian/doctrinaire conservative Westerners (the Goldwater faction). The antidemocratic people, the ones that manipulated the rules to keep a minority in power, were the Dixiecrats. They created all kinds of obstacles to prevent Black people from voting. The parties reshuffled after the Democrats adopted civil rights and the rise of Reagan shifted the balance in the Republican Party. The Dixiecrats (and non-southerners who think like them) largely became Republicans, and the Rockefeller Republicans largely became Democrats. The factions that believed in minority rule still believe it, but they are under different party flags now.