Joe Biden does not need to worry about performance; from this point forward, he is the candidate who cannot lose, no matter what. Although it is expected Bernie will throw everything he has at Biden, it is very unlikely that would make any difference. The Democrats have already made up their minds. The remaining debates for the primaries will be carried out as a matter of process; it would be like “going through the motion” but the outcome is already fixed, not by the Democrat Chair but rather by the constituents who believe Joe Biden is the candidate that has the best chance to defeat Donald Trump in the November elections.
The Democrats are comfortable with a Joe Biden candidacy. Even a few defected Republicans who are disgusted at how Trump has destroyed our system of government, trampled the rule of law and shredded the Constitution will support and vote for Joe. Most of those Republicans have said so outloud.
So, it is settled. The primaries are over.