We're already seeing the seeds being sown for blaming them for a Biden loss.
"YOU WEREN'T CIVIL ENOUGH! YOU MADE US LOOK BAD!! THOSE SUBURBAN REPUBLICANS TOTALLY WOULD'VE VOTED FOR US OTHERWISE!1!" they'll screech.
Democrats/libs will never blame themselves for losing, only others. No matter how blindingly obvious it is that their pride and arrogance cost them victory yet again.
Like Hillary Clinton, one of their gods: They can never fail, only be failed.
Depends on what libs you're talking about. Random self-identifying libs on the internet have never universally supported BLM, and I remember them openly denouncing BLM at least by the time of the Freddie Gray protests.
But if you mean PMCs, party officials, and elected Democrats, I'm pretty sure they'd just blame Bernie Sanders and "bernie bros" again, maybe with something about antifa thrown in for good measure. And then there's always Russia and, conversely, the actually legitimate problem of voter suppression. They won't even have to turn on BLM to denounce the protests, either, even if they had the balls to do it. They'll just push the narrative that white people from out-of-state are the ones causing all the violence, on both sides of course, and call it a day.