And I thought it was significant to see it drop to 424, figuring that from now on the changes would be small and gradual. He was at 440 or 443 just a few days ago. That is a very big drop. I think the constant pressure is having an effect, especially on those who are supporting him but were refusing to check behind the curtain. It doesn't really take much more than a glimpse to learn (A)the things he admitted to doing and (B)that he has been misleading his remaining supporters about it.
It's tough to support someone with his issues and his way of dealing with them (lie, misdirect, bully people, use his family as props, etc). There are 401 people who either have not yet looked into what is going on, or who will stick with him to the bitter end. My guess is that there are a lot more of the former.