I used to be a strong believer that Jane was Red John but they are writing it to be impossible for him to be. The one thing I can't get passed though is when Jane has the hallucination of his daughter and she looked him in the face and said do they even know who you are and Jane has the sheepish guilty look on his face.
Can't see many (which I find quite surprising) pointing to this:
Patrick Jane's dad - Alex.
1) They had a falling out approx. mid 80s (not long before the killings started) where PJ ran off with a fellow carnival worker (his now dead wife). We've barely seen Patrick's past relationship with his father since then, so there's no reason why there can't have been reasons why him running off with her might have caused even more issues (maybe it was the final nail in the coffin of the father/son working relationship).
What we do know for fact is that their relationship broke down because Alex cared little about the people they were hoaxing, and PJ did (more so) which ruined some of their work.
2) Alex realised PJ was the better psychic but as mentioned, they fell out about ethics more than anything. Cue years later when PJ is then suddenly making himself famous and a decent living doing exactly what his dad wanted him to do all along.
3) Alex would fit the right age group, will have no doubt shaken hands in the past, and would explain (whoever it was that said it) saying Red John and Patrick Jane are very similar. Almost every clue we have can be seen in Alex.
4) There's no real 'down side' to the story in terms of feeling like "oh man I liked them" or "what about that episode when happened?" - and it isn't 'obvious' like some of the other top suspects are which I doubt the writers would go for.
We also have a lot of scope in which to further develop the relationship without giving too much away about how it might be his dad.
Thoughts!?