Joe Biden had a great night on Tuesday and is now in the lead for the Democratic nomination. Unlike Sanders' earlier lead, which seemed tenuous to me, Biden's current lead feels much solider and could well hold up. Still, a long way to go and Sanders isn't out of it yet.
But it seems to me that his theory of the case has taken some huge hits. Surge of youth turnout?. Nope. Blowing past his earlier one quarter to one third ceiling of support? Nope. Expanding his base beyond the most liberal elements of the primary electorate? Nope. Bringing in black voters with his populist progressive vision? Nope.
Instead we had Joe Biden winning 9 of 13 state contests with significantly higher average vote totals than Sanders and generating turnout increases in suburban areas where animus toward Trump runs high and interest in Sanders is tepid.
In short, voters really, really want to beat Trump and they are deciding that Biden is much better positioned to accomplish that job than Sanders. As I've said a number of times before, the central task of a 2020 Democratic candidate is to turn Trump disapproval into Democratic votes. Biden, voters are saying, can probably do this fairly effectively; white Sanders seems like quite a risk.
As for turnout, forget the youth thing. The most important driver of driver of turnout in 2020 will be Donald Trump and how Democrats feel about him. That's what the Super Tuesday results are telling us. And really, why did anyone ever think anything different?