So he is taking your picture. Legal act in public areas. Should thank him for documenting that there are real people signing the petitions.
He is only attempting to provoke a situation they can spin to their advantage. Even telling him he's #1 ends up a "look at the kind of people we're up against". Best thing you can possibly do is make your own (larger) "Sign the recall" sign and stand next to him. Beyond that, ignore him.