The most obvious possibility is AOC. In that case I am sure she’ll move even further right and get totally ratfucked by the party regardless. That’s the most jokerified option, I think. At the very least, her obvious ratfucking will push many more people to the left like the Bernie campaigns did.
But the worst possibility is some rando Democratic apparatchik we’ve never heard of like Mayo Pete showing up. They take up all the aesthetics of Bernie’s campaigns, they receive the glowing endorsements of Bernie and the squad, but they seemingly refuse to outright promise anything we would call “good”, and they suspiciously receive no material push-back whatsoever from the Democratic party establishment other than some clearly bad faith grumblings about how spooky and radical this person is. Win or lose, they completely suck the energy out of leftist movements in the imperial core for a further decade.
Yeah, Bernie was a potentially huge force in American politics around that time. A local politician from around here even went over there to support his campaign, and used that support as a proud badge of honour in their own election campaign. People liked Bernie, not just in the US. A lot of the rest of the world looks on in horror at the way the US is run and we would love to see a government there that cares about the people.
I think the whole Clinton thing is important to remember, it was far more important that Bernie lose than Clinton win.