It is the age of their ideology rather than their physical age that is worrisome.
What do we mean by the age of an ideology? The time since a set of public policies was adopted from a given set of facts. Some ideologies are self-updating. You can think of them as having version numbers (Major.Minor.Patch). Some ideologies never had a major update.
All political parties face the risk of falling out of sync with reality but ideological movements face a further challenge. They must update their legacy code. They cannot go greenfield.
This legacy code is called "gains". It's stuff Sanders or Warren can't get rid of, even if they suspect the code is wrong. They carry it on their backs like a burden for the sake of backward compatibility.
Eventually ideologies become accretions, like those tinker carts of old, holding assortments of policies, subsidies and special benefits sticking out like bits and pieces from every nook of the lumbering conveyance.
Mature ideologies can become extraordinarily rigid. How do you reform Chicago? If the answer is burn it down and start from scratch that's not reform. That's revolution. The challenge is how to achieve change without resort to that.
Perhaps the only model with a chance at peaceful transition is supercession. Somebody builds a parallel system and users migrate until nobody is left using the legacy system. It happened to the telegraph. Nobody sends them any more.
