inherently unstable. And that is true because of the nature of Leftism itself.
Think about it: Conservatism is empirical in nature. Its focus is on what has worked in the past. So the past is key to understanding the world.
Leftism, OTOH, is based in a Continental Rationalism. As such, it is NOT rooted in what has worked in the past, but on what seems to make sense now. And that changes from day to day. It changes with every trend of Lefty doctrine. It is the wind. For a Leftist, let the evidence (and thus the past) be damned!
So inherently, Leftism is as unstable as the current fad. Ask the Soviets (and all Leftist regimes)–what is good today and that same thing may get you the firing squad tomorrow! Styles change, and so does Lefty doctrine (except at the violent core). It is the sand shifting under your feet.
In other words, Leftism is inherently unstable. I mean, your kinda Lefty parents and grandparents would gasp in unbelief at hearing what a Lefty believes and endorses today. But the same is simply not true for Conservatives–certainly not nearly to the same extent, anyway.