Let people vote for whoever they want. Whoever you have in mind to replace him will probably not live up to expectations.
Beside, I think he has a shot. Usually when votes goes hard right they usually go hard left next time.
What does this mean? Is there someone suggesting that people can't vote for whoever they want?
After lots of complaints, the process was completely redesigned in 2018. Now, the candidate to get the majority of delegates becomes the party nomination.
Since Bernie has been clear as an actual candidate with potential to win, some democratic members have been caught speaking about returning to the superdelegate system [0].
Some believe Bloomberg's surprise entry in the race are an attempt to "crack the vote", that is, ensure that enough people vote for Bloomberg that Sanders does not win the majority, in which case the superdelegates are the tiebreakers to pick the nomination. This theory is very loosely backed up somewhat by an overheard phone call with John Kerry advocating him to join the race, to stop Sanders. [1]
[0] https://www.politico.com/news/2020/01/31/dnc-superdelegates-... [1] https://www.nbcnews.com/politics/2020-election/john-kerry-ov...
How can we know that? Because that's precisely what happened in 2008. Hillary had tons of superdelegates lined up behind her when the primaries started, but then Obama got more votes, so the superdelegates switched.
If you recall the last election, almost every poll said Clinton would beat Trump.
I wouldn't put much faith in the polls, especially this far out.