Definitely think it's Mashburn. And I have since the moment he was first introduced as a character on the show. And for me it's not just the power and the affluence that make me think it's him; more than anything it's the charisma, and personality. Because the power, and the affluence and the fact that he wears a lot of red shirts (and even the fact that he slept with Lisbon) could all just be a coincidence, false clues Bruno loves to set up for his fake RJ suspects. And especially with Bruno Heller, it's extremely important to be vigilant and take everything with a pinch of salt - despite Jane's declaration (I think it was Jane?) that there are no 'coincidences.' I mean, I don't know if it's just me but I've really begun to become very careful of the 'clues' to RJ and all of the different 'plausible' suspects, because they are only plausible because they happen to coincide with what we've heard of RJ from others. (For example those saying it's Brett Partridge because of the voice similarity and the fact that Partridge is also the name of one of W Blake's paintings, or people saying it's so-and-so because of their age, look, height, money, etc. Or people saying it's so-and-so because they also shook hands with Jane.) Listen, similarities like that could all just be mere coincidences planted by Heller to mislead us, and thus they can easily be refuted. Which is why I don't want to go on about the fact that Mashburn has money and affluence and thus that fits RJ bc it could just be a coincidence. Also why I don't want to go on about how he wears red shirts and slept with Lisbon, one of Jane's 'loved ones,' because those could easily just be coincidences too, "false clues" put there by Heller to mislead us into thinking he's RJ bc he fits the 'part'. Once again, we have to remember that while RJ is playing mind games with Jane and misleading him, Heller is doing the same with us by always integrating new evidence about RJ and new possible suspects that could 'fit the part.' So it's easy to get lost and find yourself, after several seasons of the show, with a long list of suspects just because "it could be him" because "he also has so-and-so, like RJ does." That's a trap! Heller probably has 2 more seasons, so trust me, there's always going to be new evidence about RJ, and you're going to consistently find yourself trying to match what you've heard about RJ with people you've seen on the show, and by the end of it you'll be left with a long list of people who could only be RJ bc of a number of things they have in common. And then you'll be more lost than ever and won't know what to do. Actually, proof of that is the number of RJ suspects, and how immense the RJ file is. It's basically a compilation of everything found about him ever, tied to trying to match that with people who fit that 'criteria.' Proof #2 is that this is kind of the trap Jane is himself falling into now. (Especially in most recent episodes.) He's taken 'shaken hands' very literally, has made a list, and he is matching everyone's he's met to that list to narrow it down to a few. It's a vicious cycle that he - and we - are falling into. And it's one I'd like to avoid because then my theory would easily refutable; the same way I could easily tell anyone saying that, for instance, Ray Heffner is RJ because he was a member of Visualize in 1988, and the name 'Ray' is similar to 'Roy', that it could just be a coincidence. A false little one to misguide us into thinking he could be RJ. But as I said before, the problem with that, is that if we proceed that way, anyone can easily become RJ, because we're simply compiling clues. And then we end up with a never-ending list of suspects. (Which is what has been the pb with the RJ case all along, obviously. It's not that they know who he is and can't find/catch him - it's that they don't even know who it is yet. Their suspect list is too long/vague.)
However, one thing that cannot be refuted is someone's personality. And that is why I think Mashburn is RJ. He is the strongest character to have all of the 'personality' qualities similar to those described of RJ. And he is definitely likeable and attractive - he has this 'je ne sais quoi' that draws you to him. He is a good conversationalist, has a way with words, and loves to play games. Honestly, there is no one we've seen on the show so far more fitting. But more than anything, he is extremely, extremely similar to PJ. And that is the main quality described of RJ throughout the series consistently (and so it cannot be a false clue): that he is similar to PJ, and has a lot of his traits. Mashburn is exactly that - he loves the thrill of misleading, just like Patrick does. He loves the mindgames, like Patrick does. He is incredibly smart and perceptive, just like Jane. He loves judging people and outsmarting them, and he does it with such subtlety and prowess that even Jane doesn't doubt or suspect him. It's really insane because I saw the minute they met how strangely similar they are, and yet I was surprised Jane didn't pick up on it. No surprise Lorelei said 'I only wonder why the two of you didn't become lifelong friends the moment you shook hands' ! But more than that, they both have fun playing with people and their perceptions.
What's interesting to me is that Jane is so blind when it comes to the RJ case because it is personal to him, obviously. Nevertheless, it's weird because although in this case, he's been extremely 'police-like' by assimilating evidence and 'routining' it out to find out who RJ is, that's not how PJ usually is. Usually, when he's solving cases, he picks up on a small detail and goes with it, or, in most cases, he goes with his gut and follows his instincts, rather than facts and hard evidence. That's what makes him different - he finds out who it is based on how he feels about them, and what he senses. He doesn't listen to the facts. But what's interesting here is that with the RJ case, he's doing the opposite and not being his usual 'mentalist' self. Instead of employing his judgment and instincts to guess who it is and retrace his steps, he's in a way following protocol and simply assimilating evidence. (Especially in the last episodes, now that he has his little book with a detailed list.) And I feel like that's precisely what he needs to be doing - because by following evidence, he'll constantly be mislead, and RJ will always have the upper hand and be one step ahead of him. BUT if he drops this crazy list of 'everyone he's ever met or shook hands with' and actually starts following his gut and dealing with the case Mentalist-style, he might get somewhere! I mean let's be honest, what better way to deal with someone who plays mind-games than playing mind-games back? You gotta outshine him at his own game, PJ.
Anyways, bottom line, I do strongly believe it's Mashburn because I think his personality has something going for him that is impossible to deny. And I'm not going to lie, if the show ends and it's not him, I will be extremely disappointed. But we'll see! 

Okay, switch The Mentalist back to Sunday so I don't have to wait 2 weeks instead of 1. Switch it back! We have been waiting to find our who Red John is for 5 FRICKIN' YEARS. COME ON BRUNO.

I suspect that Bret Stiles has a son who is Red John. I find it hard to believe that Stiles doesn't know the identity of RJ seeing that he has given Jane info on where to find Christina Frye after RJ took her. Seeing that RJ kills (or has killed) anyone who has been compromised. That fact that Stiles is still alive means that he is trusted by RJ. A young inexperienced killer at the barn on the farm that Visualize operated points to a member of visualize and Stiles doesn't seem like a man who leaves loose ends so he is protecting RJ which means that RJ has to be especially important to him.. like a son would be.