I'll second and piggyback some of the previous Minelli posters, who make good points.

Go back and watch the early episodes, they're a better indicator of the true essence of the show.

Opening title sequence - Mentalist - def. - A master manipulator of thoughts and behavior.

Jane is not going to get Red John by suspects being eliminated one by one.  It shouldn't be the butler with the candlesticks in the pantry.  That would be very disappointing to me.

He is not behind Red John, he is one step ahead.  This is high level chess, not a Milton Bradley board game.

Much more satisfying for the audience and truer to the character of Jane is a gambit - def. - a chess opening in which a player risks one or more pawns to gain an advantage in position.

The carney performer with the brilliant mind is performing master manipulation.  Don't pay attention to the misdirection or the sleight of hand.  Who's whistling or who's afraid of birds will not lead to the endgame.  Red John made a mistake, and Jane will press the advantage, perhaps the audience isn't even privy to that information.

I wouldn't hold it against Heller if he's not being completely forthright with the list of suspects.  Deceit is a part of manipulation.  It has reengaged the audience, and let them know there will be a Red John payoff. 

Minelli is a good suspect as others have pointed out.  I would only say the last episode of season 1 casts a lot of suspicion on him.  He's the one who pointed out Tagliaferro translates to "cut iron" which led them to Sheriif Hardy's farmhouse, which Red John was trying to lure Jane to.

Could Minelli have been Red John in the farmhouse room calmly sipping tea taking in the whole scene?  Very possible.  His age fits with being a friend of Hardy's father.

From Heller's perspective, it's possible The Mentalist was not going to be greenlighted for season two.  He could've completed the story arc after 23 episodes by having Jane confront Minelli at the farmhouse.  Remember Jane was onto Hardy, and was willing to sacrifice his own life to draw out Red John.

How is it that Red John has so many followers and disciples who do his bidding and are willing to die for him?  It can't be all because of his devilish charm and powers of persuasion.  He has extreme leverage on them some how.  If wicked, Minelli as the head of CBI would have that leverage.  The law enforcement connections, who gets promoted, who gets a job.  If discovered, the power to send depraved criminals like Timothy Carter to jail for life - or as a reprieve from Red John, a second chance at redemption.  Seems like we've heard many of Red John's followers paraphrase words like that.

That's my two cents, really enjoy the website and people's different theories.  Some stuff I never would've thought of - Ellis Mars - playing a bumbling psychic in plain sight - "He is Mar" Spanish translation - "El es Mar" - went right over my head.  I'm going with my first instinct though and sticking with Minelli.

Do what you have to do Patrick, rooting for you mate