I think it is Sheriff Thomas McAllister. He is only the Red John suspect who's age has been pulled down from his real life age. He is really 57 but in the show he is 50, it seems like they are trying to make him younger to fit to be Red John. Why didn't they change other characters ages? Why only him? 

He is also the most unlikely suspect that we think he has no possible reason to be Red John. Just like in all of the episodes of The Mentalist, we only know reasons of the suspects to kill whoever has been murdered and we only find out the reason of the actual murderer when he explains it when he gets caught by Jane.

He and Ray Haffner are the only suspects out of the seven who has appeared with the word ''Red'' on the title of the episode. Also the case of the married couple in S1e2 in Napa connects to the story of married couple Timothy Carter and Sally Carter. And on the next episode of Mentalist they are going to focus on Thomas McAllister and things will happen that has no connection with Red John but I think that the things that will happen will make sense when they slowly get closer to Red John.

The RJ case has to be more complicated than a lone psychopath with loyal followers.  The notion that a psychopath is going to have numerous companion psychopaths or even just willing followers who are willing to die for him seems far-fetched.  Also, it would be trite for ALL the law enforcement agencies -- Homeland Security, the FBI, the CBI, and even local PD's -- to be widely evil, corrupt, and incompetent  except! for Lisbon's virtuous, heroic group.  (A major purpose of internal affairs departments is to root out corruption within those agencies, no?)

So, despite Mr. Heller's misdirection and focus on the RJ identity, the more interesting question centers on the motivation and involvement of the other major characters and organizations.  Here are some possibilities.

o  OPERATION TO NAIL VISUALIZE - What if Homeland Security, the FBI, the CBI, and even local PD's are pursuing RJ, who is closely connected to Visualize?  Visualize has numerous supporters within law enforcement so the agencies would have to run a top secret operation.  Hence, Bertram and Kirkland appear to be conspiring against J's hunt for RJ, but they are trying to protect a legitimate investigation.  J's 6-mo. absence from CBI while he was in Las Vegas plus his involvement with Lorelei would give them reason to wonder whether J had been co-opted and might help RJ.  (If Bertram and Kirkland were RJ supporters themselves, why would they ever wonder if they could "trust" Lisbon, as presented in S5E16 "There Will Be Blood"?  Knowing Lisbon is close to J, they could reasonably wonder about trusting Lisbon when they had doubts about J.)  The seemingly shady, conspiratorial behavior of Bertram, Kirkland, and Smith would then make sense for legitimate reasons, rather than just as pawns of RJ.  RJ would then likely be Haffner because of the Visualize membership.

o  RED JOHN IS ONE NODE OF A LARGER INVESTIGATION - Another possibility is that RJ is just one node of a much larger legitimate investigation by Homeland Security and the FBI.  I'm intrigued by the international reach of Visualize and RJ.  Remember that Montero, friend of Todd Johnson and RJ, did gun running to Central and South America (S3E16, "The Red Queen").  Sean Barlow (S5E22, "Red John's Rules") was a compelling character from PJ's carnival days.  As mentioned by Pete Turner (PJ's carny friend), Barlow maintains connections in Ireland.  Barlow is old enough to have been involved with the IRA (Irish Republican Army).  Although the IRA is politically disbanded, the network that used to fund it supposedly is still active in crime and had/has links to other terrorist organizations (FARC in Colombia, the Basque ETA, Libya when under Quadafi, and the former PLO).  Kirkland could have killed Jason Lennon (S5E18, "Behind The Red Curtain") because he was a covert agent who had been "turned" by RJ (per Kirkland, Lennon had become a "plaything of monsters") and needed to be eliminated to protect the larger investigation.  (BTW, Lennon seemed aware that Kirkland was about to kill him but did not cry out or object.  That suggests that Lennon accepted Kirkland's judgment that Lennon would spend the rest of his life in prison and, perhaps, that being killed was an easier and even just consequence.)  The conspiratorial behavior of Bertram, Kirkland, and Smith again would make sense for legitimate reasons.

o PERSONAL CONNECTION BETWEEN J AND RJ - Finally, having J's involvement with RJ go back to J's carnival days, to his past, would make for much more powerful drama.  RJ's obsession and special treatment of J seems far more personal than just a reaction to J's on-air comments about RJ from 10 years ago.  Again, I was intrigued with the Sean Barlow character.  According to J's carny friend Pete, Sean Barlow cultivates grudges, would not hesitate to kill his niece, and is "a sinister piece of work -- mean and clever" (S5E22 "Red John's Rules").  According to J, Sean Barlow was close friends with J's father till they became enemies (S5E22).  Wouldn't it be interesting if Barlow pursued revenge against Alex Jane by attacking his family--J?  The S5E5 "Red Dawn" episode in which Judge Dellinger says, "If you want to hurt a man, don't kill him.  Kill his family" establishes that perspective on revenge.  IF Sean Barlow pursued revenge against Alex/Patrick Jane, AND if RJ were an agent/friend of Barlow, AND if Barlow and RJ were also involved with international criminal/terrorist organizations, THEN there would be reason for the interest and involvement of Federal law enforcement/security agencies in what is seemingly a local serial killer.  The various parties would also have cause to wonder about J's allegiances.  J would be connected to Sean Barlow, known to be involved with criminal/terrorist organizations and a former business partner of J's father Alex.  That could even explain Kirkland's initial warning to Minelli (via Alexa Shultz) about J when he was first hired by CBI (S5E5 "Red Dawn").  True, J's family was killed by RJ, but then RJ's mistress Lorelei became J's lover.  An outsider could have cause to wonder about J.

IMHO these scenarios are more interesting than a local psychopathic serial killer annoyed by an entertainer's on-air insulting comments ten years ago.

Thansk for reading this.

Some thoughts about the last episodes.
First I think Red John's
identity has been desided almost from the start and every trick the
writers play is for making every posibility plausible until RJ is
revealed. The list of suspects is one of those tricks, and it's classic.
So
i think that through the 6th season we will wittnes a lot of tricks
similar to the ones magicians use to draw our attention away from the
important detail that is happening at the same time, and we fail to see it!
In the second episode of season 6 there are at least 2 of those magic tricks:
1)
Lisbon is in the bed at the hospital talking to Jane. There is a knock
at the door and a nurse-doctor asks for someone Carmen Lee. We can see
Jane turning to look at her and he puts some thought to the incident.
Ok, now right after that Lisbon reminds Jane that RJ reached in his mind
and killed a happy memory of his! Right after he exits the room he
tries to reach Sophie on the phone. He also happens upon that same
doctor at the corridor and he doesn't give her any more attention.
So
I think that Carmen Lee is the trick. It's a random event with no
significance that makes as think that it's the reason he remembered
Sophie Miller. The truth is that the idea to look for Sophie was planted
into Jane's mind by Lisbon when she reminded him of RJ killing a happy
memory. Later on Jane is in bed looking up and he gets a flash-back of
Sophie. It's a happy memory one would think. Well I don't. Take a look
at episode 10 of season 1 again. The flash back is from that episode. If
Jane was recalling a happy memory, it would be something like the flash
backs he has in that old episode. That is of Sophie helping him at the
asylum or him and her saying goodbye. But what do we get as a flash
back: Jane and Lisbon meating Doctor Miller! Moments later Cho asks Jane
if he is still working their case and he answers "always!" Oh yes. He
is always calculating all possibilities!
2) Second trick same
episode. The scene at the park. There is nothing more common in parks
than a lady feeding pingeons. And yet we have a lady who looks very much
like Partridge sitting on a bench next to them feeding pingeons. Well
it's a random event put there to full us. We get to think that it could
be RJ just because we saw pingeons at the end of the previous episode!
But something very important is happening right there and we may mis it.
Jane makes Lisbon think they sould look for Sophie's files and maybe
they find clues that RJ went to see her before. Have you noticed that
Jane hides the fact that Sophie only taped sesions and didn't type them!
He hides the fact that sophie's recorder is allready in his pocket!
Why. Did anybody noticed that or we just looked at Jane looking at the
pingeons? Later when the team fails to find any file on RJ visit to
Sophie, Jane pops Sophie's recorder and acts like he fulled RJ. Well it was his team that he fulled.
3)
And lastly I noticed something that looks very unexplained to me. Jane
breaks into Sophies house. he walks to her desk. On it we see a photo of
her with her dog. So we assume she's single. Jane can assume the same
but Jane can know even more that what is obvious to us. He's smarter.
Next he looks into the fridge, then he reads the note on the fridge and
then he opens the oven. Ok, for a moment let's go back to episode 1 of
season 1. The pilot. Jane explains to Partridge at the crime scene that
RJ thinks of himself as an artist. First you see the bloody smile and
know they are dead and feel the terror and then you get to see the dead
body. That's exactly what RJ did here, but Jane fails to see the RJ
smiley on the same note that says "dinner's in the oven" and gets
surprised by the head in the oven. That i can explain. This is not our
Jane. Jane looks at what you ate for dinner and he knows right there
that you killed yourself for honor! At least I find this very strange.
Also have you noticed that Jane took Sophie's recorder before finding
her dead? It would make more sence if he took the recorder of a dead Sophie not a living one!

So any thoughts?