Rise of the New Left

[Mr. Morden]

I'm skeptical we'll see a major party die in our lifetimes considering how entrenched they are, but I really would love to see the GOP die.

Beinart isn't actually predicting that though.  He just argues that the political center of gravity will move to the left.  That doesn't actually mean that the GOP is going to die.  The GOP could adapt to the new reality over time, and remain competitive.