The more I re-watch the episodes with red John the more I lean towards Brett partridge. I think he is red john and he swiped Theresa off her feet. His right hand man (haffner or kirkland) drew the smiley face on Lisbon.

Partridge's character evolves thru the series which I think is strange for such a minor character. He starts off as this hyper, macabre, irritating nerd but by season five and six he is more composed. He just seems different. Almost more grown up and confident but still totally creepy.

My second choice is Haffner. If it ends up being Mashburn that would be awesome too. Tbh if it ends up being anyone other than these three, I will be disappointed.