In this case, I think the Democrats are analogous to the Whigs. There are very few, if any, centrist Dems left. They keep the name going, but they are now the “Progressive” (read New Socialist) Party. The Scoop Jacksons and Joe Liebermans have indeed faded away.
Well, it’s a debatable point. But you have to compare the actual longevity of the parties.
The Democrat party, then, as now remain pretty much in lockstep on a statewide and national basis as they have since the days of Andrew Jackson when they competed with the Whigs.
The Republican Party as a party however, may be facing a cataclysm that will indeed break up the Party as an organization since both the Trumpsters and many in the other half of the GOP have stated that their continued allegiance depends on the nominee.
Both sides predict/threaten Armageddon if they don’t prevail
If that remains true, then no matter who is the Republican nominee, Hillary will be elected and the values, economics, laws, and culture of America will be transformed for decades if not forever.