I think there are several factors involved. The left has lost its original mandate - a fairer economy, and it has been replaced by identity polirics for minorities. A lot of that has become very extreme, and central dems are either going to abstain or vote for Trump.

Also, the DNC, is 'owned' by neoloberals, and they will not allow a socialust to be nominated. That is why young people are moving away from Biden.

What is needed is several things.

1. The borders need to be closed.
2. The weapons industry needs to be limited
3. Certain criteria need to be put in place before people can run for president
4. The government needs to foit the bills for candidates running.
5. No candidate allowed more than 4 periods in office.

And so on.

If course, it won't happen. Too many corrupt people in office.