It would be interesting to be able to run a parallel campaign where Hillary never returns to the campaign trail and only relies on surrogates. Would this Hillary-less campaign run better or worse than the real one? Certainly no worse. Consider how everything that made the Democratic convention such a success had nothing to do with her.
But, actually, Hillary is such a non-presence that it might be hard to tell the difference between this hypothetical experiment and the campaign she’s been running. It’s an odd year: The Trump campaign is conducting an experiment in whether it’s possible to elect someone president without really having a campaign; the Clinton campaign is conducting an experiment in whether it’s possible to win a race for the presidency without really having a candidate.