What's changed is the needs of the political classes. The democrat party has been in something of a death spiral for decades (arguably since the 50s) and is cri

What's changed is the needs of the political classes. The democrat party has been in something of a death spiral for decades (arguably since the 50s) and is critically dependant on imported voters. Without the massive immigration that has happened post-1965, the political party configuration would have almost certainly fractured and reformed along quite different lines by now. But ongoing immigration has kept the democrat party in its rather ossified form highly competitive (as they lost "American" voters, they gained immigrant votes). This is why they were so terrified of Bernie Sanders. He got a lot of support from working class whites who have been trending Republican for decades. But a figure like Sanders would derail the agenda (immigration and all) that is keeping a never ending stream of Kennedys in power.