How is it possible for someone in his position to make a mistake like this?
The risk far outweighs any convenience in copying material like this. It can't be deliberate. It's easy these days to copy something for your notes and later simply mistake it for something you've written. It's also possible that someone else, someone untrustworthy, ghostwrites for him. Or perhaps there are talking points floating around in email and both LePore and Zakaria cut and pasted the same thing.