No matter which it is, however, we should be under no illusions: if Biden steps down, either due to necessity or perceived expediency — it will be a Very Bad Thing. It will be an even bigger gift to Donald Trump that the current discourse. It may very well ensure that he wins the election.
My thoughts have started leaning towards this line of thinking by Craig, writing at Cup of Coffee.
No easy decision to be made, and a similar choice will be made by Trudeau before the next election.