That's some impressive stuff right there. The public generally is unaware of that sort of thing - the media does a good job of hiding the fact that most politicians resemble entertainers, same rehearsed act, day after day.
Newt has an impressive mind. I heard a similar thing about John Roberts at his confirmation hearings for the Supreme Court. The writer said that when he learned that Roberts had no notes for his opening statement he knew it was going to be a slam dunk.
Lots of entertainers keep a sort of diary with them most of the time. It's filled with stories, jokes, anecdotes..whatever. They read it constantly so as to have the data fresh in their mind if needed.
Comedians call it their funny book.
I would imagine politicians do something similar, well perhaps Newt does not.... he seems to have a photographic memory, as does Clinton.