A majority of young Democrats support Bernie Sanders. A majority of not so young Democrats support Hillary Clinton. The generation gap is not surprising at all. People tend to move right as they age. Older people note that we have learned to compromise and deal with reality. Younger people note that we have become cynical and lost the audacity of hope. But the question is why is the generation gap more marked now than it was in the 80s and 90s.
I'm old enough to remember a *real* generation gap. I remember 1972 (I even remember 1968). One explanation of the Sanders phenomenon is that people under 30 don't remember the USSR and associate the word "socialism" with Sweden not Stalin.
I think another explanation is that young people don't remember 1972. I'm a late boomer (1960) and have long been very irritated that the leaders of the Democratic party are older than me people who can't get over the mistake of supporting McGovern in the 1972 primaries.
Now I know how they feel. I am sure that Sanders if vulnerable to a negative campaign accusing him of being a socialist (which would have the additional advantage of being true). I don't trust the early general election polls at all.