You watch. The very next generation of Democrats will be full throated Marxists. Once Biden dies off along with Pelosi, Feinstein, and the other very senior Party apparatchiks, Democrats will accept nothing short of fascism/Marxism.
I agree. Organizations and movements almost never turn away from extremism once they go down that path. Unless, of course, there is an outside force that turns them away, like Eisenhower and SHAEF.
The only peaceful example I know of is when William F. Buckley kicked the Birchers out of the Conservative Movement. By doing so, he began the process of rebuilding Conservatism.
I think in twenty years Alexandria Octavio-Cortez will be considered a mainstream Democrat.