He seems to have been right that Trump's odds were higher because prediction error for different states wasn't independent as some other models were assuming.
I agree that we don't have a way of assessing whether the percentage given was "correct", but over a bunch of predictions we can keep track and see how he does when he gives various percentages, or compare against others with a proper scoring rule.
I don't make any claim that the odds he gave were right, but just that if they were we should still expect to see his "prediction" be wrong pretty often, so the fact that his prediction was wrong this time only counts so much against him (and to make up for that, only counts so much in is favor if he's right with low confidence).
I agree that we don't have a way of assessing whether the percentage given was "correct", but over a bunch of predictions we can keep track and see how he does when he gives various percentages, or compare against others with a proper scoring rule.
I don't make any claim that the odds he gave were right, but just that if they were we should still expect to see his "prediction" be wrong pretty often, so the fact that his prediction was wrong this time only counts so much against him (and to make up for that, only counts so much in is favor if he's right with low confidence).