Who would be the Democratic nominee if Biden didn’t run?

[Landslide Lyndon]

Without Biden locking down the black vote, Harris and Booker would have been real players. 

And no, Sanders wouldn't win. His campaign aimed from start to finish to get 30% and that's exactly what he got. You can't even get a sniff of the nomination with 30%. 

[Landslide Lyndon]

It'd be hard to imagine Bernie losing a single state in this timeline.

The moderate vote would've coalesced around somebody else, so probably not.

There is no "moderate vote." By all accounts most Biden support goes to Bernie.

Sanders couldn't even win a majority of Warren supporters.

[Landslide Lyndon]

It'd be hard to imagine Bernie losing a single state in this timeline.

The moderate vote would've coalesced around somebody else, so probably not.

There is no "moderate vote." By all accounts most Biden support goes to Bernie.

Sanders couldn't even win a majority of Warren supporters.

Well yeah, his base and appeal never had much overlap with Warren's. Biden's did.

It had plenty earlier in the primaries, but this is often overlooked. Ideological lanes did exist in those primaries, but they were fuzzy at best and much of the appeal of each candidate had was not directly related to it.

The only common thing Biden and Sanders had was that they were both old white guys. Other than that they were polar opposites.

[Landslide Lyndon]

I'm not at all sure, but my initial gut reaction is buttigieg. I know that doesn't seemed initially logical, and of course all this is subject to the complete change in Dynamics as to how the campaign would have progressed pre I awoke without buying as the presumptive FrontRunner for so many months.

Please correct me if anyone has statistics to the contrary, but I'm guessing a significant number of white Biden voters may have chosen buttigieg as their second choice. Buttigieg seem to do well with order Democratic whites who were liberal, but not Bernie Sanders liberal. As badly as fighting did in Iowa and New Hampshire, even winning a plurality abiding voters would have probably given him the victory in both of those close races over Sanders.

I don't think Harris or Booker would have necessarily been able to coalesce the black vote without buying. They had plenty of chances on their own when black support of buying was a mile wide and an inch deep, much like it was for Hillary during the 2007 race pre Iowa. Neither one of them could present themselves to the black community AZ a viable Contender to get behind the way Obama did. I just don't see that Dynamic changing much without Biden in the race. While I suppose either one could have held on through lousy showings in Iowa and New Hampshire to somehow pull off a black voters fuelled victory in South Carolina the way Biden did, neither of them had the national presents and name recognition that Biden does in order to survive such big early hits.

Of course that still leaves open the question of where does the black vote go? Buttigieg?!? Not likely. Warren seems only marginally more likely, and that ain't much.

I bet I mostly spitballing / $hitposting here rather than making a firm point.

Democrats were incredibly risk-averse this year. I seriously doubt they would have picked the gay mayor of a mid-sized city who had literally zero appeal to minority voters.

[Landslide Lyndon]

I can see one of three things happening. Bernie wins due to divided opposition like Carter in 1976 or Trump in 2016, Warren wins by building a coalition of enough  center left and progressive voters, or Bloomberg gets in earlier and buys the nomination.

Sanders barely broke 30% even after the field consolidated. With proportional allocation he would never get a majority of delegates. Hell, his own campaign manager admitted that their goal was to get about 40% of delegates and then strong-arm the convention to nominate him.
Trump did it because of the WTA system that favored him is critical states like Florida and Missouri.

[Landslide Lyndon]

I can see one of three things happening. Bernie wins due to divided opposition like Carter in 1976 or Trump in 2016, Warren wins by building a coalition of enough  center left and progressive voters, or Bloomberg gets in earlier and buys the nomination.

Sanders barely broke 30% even after the field consolidated. With proportional allocation he would never get a majority of delegates. Hell, his own campaign manager admitted that their goal was to get about 40% of delegates and then strong-arm the convention to nominate him.
Trump did it because of the WTA system that favored him is critical states like Florida and Missouri.

He'd likely fare better in this scenario, unless Biden not being in causes butterflies that make Warren run a significantly better campaign. There were Bernie supporters that had Biden as their second choice and vise versa, I was one of them (initially supported Bernie then went to Biden and ended up voting for him).

No, he wouldn't do better for a simple reason: he didn't want to. That's why he ran an exclusionary campaign that burned all bridges and alienated every other candidate's supporters whenever he had the chance to do so.
He wanted a rock solid 30% behind him and as far as it concerned him the other primary voters didn't even exist.