There are two potential models for a Democratic victory in 2020: base mobilization; and winning over swing voters. But is it possible to do both at once? Can the Democrats walk and chew gum at the same time?
Yes, it’s possible; Barack Obama did it. But it requires considerable finesse, and not everyone can do it. Biden, for example, is depending solely on his appeal to swing voters; for base mobilization, he will have to rely on Trump.
I can see two ways it can happen. Option #1 requires a nominee who is young and a minority (to boost turnout among apathetic identity voters) with a moderate ideological program (for swing voters). Option #2 is the opposite: a white guy who connects with reactionary workers for identity reasons, but who has a radical program to mobilize the base.
Option #1 sounds a lot like Harris, if she can persuade everyone she’s really a moderate at heart. Option #2 would be Bernie Sanders if he would make concessions to reactionary white workers on cultural issues–but he hasn’t. Note that neither description fits Elizabeth Warren, who can fire up the ideologically-committed blue base, but who has no particular appeal for minorities or moderate swing voters, so her chances of winning a general election would depend almost exclusively on mobilizing millennials. That could conceivably work, particular in an economic downturn, but do you want to bet the farm on it?