A substantial fraction of centrists would have to swing one way or the other to be a deciding factor. Further, it’s always possible that if a given candidate is generating the sort of enthusiasm that amps up one side’s turnout, then more swing voters might reject that candidate (as too liberal or too conservative) and swing the other way.

That’s the question for now. The swingers don’t appear to have swung yet, and they may not. If they split….