President Lincoln was well-known for his folksy anecdotes and humorous asides. If you knew anything of real history, you would know this too.
Whatever "manner" he had in public, Lincoln was probably the best writer that has ever held the office, with a towering intellect. If you knew ANYTHING about real history, you would know this too.
Sarah Palin didn't write those jokes, Leno's staff did. She just read them off the teleprompter - isn't that ironic?