There's nothing to admit. If he actually "gets worse" as you say, then it will be time for the 25th Amendment.
OR, he will stick around through 2021 getting the ship righted again, then step down and the right-wingers worst nightmare becomes President of the United States of America, and she gets to pick her VP, OMG

I think it funny that the trumplings try making Boden look bad while forgetting what would happen if he says he is retiring, good grief they are stupid People. The righties better hope he makes it his full term otherwise they are F'ing screwed.