If there are debates - and if he is in them - and if they don't keep him off ballots - and if they don't kill him...
That's a lot of if's, already. But IF those things were to happen, he will have an impact. Dems will toe the line, but a large amount of independents have had enough with both parties.
And if leading into election day, the press can no longer sell the plausibility of a Biden win, then, he'll have an impact.