The writer is probably correct in the final analysis, but maybe for the wrong reasons. If you take a look at the Dem. Polls, even though Biden is the leader, one must take into account that many of the candidates will eventually drop out. I can’t envision the votes of those that drop out going to Biden. They most likely will collect around one of the Candidates that appeals to the Left Wing Base and that isn’t Biden. Just do the Math and if it ends up as Biden against one or two “Pro Socialists”, Biden loses.
No. Bernie when vanquished lost 2 of 5 to Trump.
Other examples: Buchanan when he quit the GOP, those voters came home to Bush. When Jackson quit in '88, those voters went to Dukakis or sat on their hands -- they didn't go to Gephardt (or Biden LOL!).