From a poll issued in January of 2018. This show that the largest percentage, 39%, of Americans describes themselves as neither Liberal or Conservative. If you assume that this 39% are mostly moderates then they would more than likely prefer Biden over Bernie.
"When asked to describe their political views as "very conservative, conservative, moderate, liberal, or very liberal," 35 percent of American adults in 2017 identified as conservative, while 26 identified as liberal".
The reality is that the country about 1/3 of each. Those numbers don't surprise me because there's a larger number of liberals who think they're centrists than there are conservatives who think they're centrist (simply look at the non-Fox News media).
The binary parties have a floor. The Democrats could nominate Stalin, and he'd get at least 38% of the vote. Remember that Mondale - as horrific a beating as he got - still got 40% of the vote despite losing by nearly 17 million ballots and carrying only one state plus DC. Goldwater go 38 and Bush 1992 got 37. My goodness, Alf Landon in the depths of the Great Depression where it was better to be dead than Republican got 36.5%. So basically there's a floor of right at 37-40% even for the most hapless candidates. The Democrats could nominate Roy Moore for President (yes - I said the Democrats) and he'd still get about 38% of the vote, maybe more. The Republicans could nominate Pelosi, same thing.
But Bernie Sanders brings a completely different problem.....namely, as 92tide keeps pointing out.....he's NOT a Democrat!!! This is the kind of thing that could cause all kinds of problems in Convention assembled.
My take on Biden is not that he's an irresponsible choice - he's not. In fact, I think he's a good choice. I also think he's the kind of guy who if nominated will see young people do the same old "ah, he's an old white guy like Trump."
The other place where - respectfully - I think your analysis is incorrect. In a world located inside a vacuum and consisting primarily of logical people without cognitive dissonance, I think you're spot on.
But that's not the world in which we all reside (and despite some legitimate carping about some of Trump's base, this is NOT just a right-wing rubes problem). In both 2008 and 2012, comedians were able to make hay by asking folks who they were for and then reciting the positions of the opposite candidate. In 08, it was Obama voters I saw make complete fools of themselves, several voting for him (or saying they were) because "he's pro-life." In 2012, the same skit was used on Romney voters with the same results.
Unfortunately, most of the safe and electable politicians cannot get the nomination (see Muskie 72, Bayh 76, Bush 80, Gephardt 88, Kerrey 92, McCain 2000, Edwards 04).
