Jackie Earle Haley was originally a child actor in film like Breaking Away and Bad News Bears and its many sequels. He like so many child actors though soon disappeared after growing up, after appearing in less and less films of any sort of note. Haley though came back almost out of nowhere with All the King's Men and then he fully made a come back by not only appearing in this role in a fairly prominent film, but also being nominated for an Academy award for his performance. Haley was nominated for, which actually is not a particularly popular Oscar character, portraying a man described as a child molester who served time for indecent exposure to a minor.
Ronnie is naturally ostracized by the community and constantly harassed by a former Police Officer, and the only person who offers him any sympathy is his mother. Jackie Earle Haley portrays this role, which very well could be portrayed in a numerous ways many which could be very over the top, for an entirely realistic fashion. Haley never for a moment tries to throw any sort of flash into his performance, like say Stanley Tucci did in the Lovely Bones. Haley instead tries to play the part as close to the bone as possible, much like in the same way Stuart Whitman portrayed a similar but also very different character in the Mark.
Haley never overplays or underplays any aspect of Ronnie in the film. He never tries to make him into an overly creepy character, even though Ronnie certainly guilty of acts deserving of such creepiness. He also does not ever try to make him into an overly sympathetic character even though he faces such harassment and only has a single person who cares for him. Haley does not try to make him either just a sympathetic or just a creepy man, instead he tries to show him as just a man with a serious dysfunction. Throughout the film, and every act of Ronnie's Haley only ever tries to show it as the natural actions of this man no matter what.
Ronnie actually is not used all that much in the film it takes him a great deal of time to appear in the film, and even after this he only has a few scenes of length that are devoted to his character. No matter what the scene is though Haley stays true to his portrayal of Ronnie. Whether it is one of his scenes that are to be more sympathetic with his mother, or one of his creepier scenes such as the end of his date. Haley always shows the same man either way. He always shows that whatever does this is just Ronnie as the complex man he is whether he is doing something horrible, or just being the son of a loving mother. Haley is consistently good in the role because he never tries to portray his character incorrectly to be more sympathetic or creepier. He never tries to make him a villain or a victim, and instead consistently is completely believable in the role and finds the truth of the troubled Ronnie. Haley is always believable in the role playing his role in the right fashion.