Gary Oldman did not receive an Oscar nomination for portraying Lee Harvey Oswald in JFK.
This film has a terrific ensemble and frankly the academy could have just nominated Tommy Lee Jones, Joe Pesci, Donald Sutherland, Jack Lemmon, and Gary Oldman as their five nominees and it would have been a much better line up than the one they decided on. The academy only nominated Tommy Lee Jones as the enigma of a man Clay Shaw, Gary Oldman I would argue plays even more of enigma than Shaw in Lee Harvey Oswald the actual assassin of Kennedy or in this film's view the man the public was given to be the actual assassin. Oldman's performance is almost entirely in flashback and many of his scenes are mostly done in heavy film filters done within many cuts usually.
Oldman does something quite extraordinary with his performance which is simply fades into the role. In all honesty the first time I watched the film I never saw Oldman and it seemed like they were using stock footage of Oswald sometimes because of how good Oldman is in the role. Physically and vocally he just becomes Oswald in what must have been some big lifting by Oldman but he is the definition of natural here. Honestly the idea of someone playing Oswald is quite troublesome as someone playing it poorly could have stuck out quite unnaturally, as I would say Brian Doyle Murphy does in the role of Jack Ruby does. Oldman though absolutely just fufills the role in such a brilliant fashion that he is able to create Oswald even in the briefest of glimpses.
Oswald is actually the biggest riddle in the whole film filled with such character. There are other mysterious characters like Dave Ferrie and Clay Shaw, but you learn far more about them since you actually get a chance to see them in the present. Oswald is only ever in the past. The film delves into Oswald as many many things. The presents him as the possible assassin, a full on patsy working directly with the conspiracy, or maybe the man determined to be the patsy after he no longer wished to be one. He also may be a communist, a government agent, or just a deeply disturbed fellow. Oldman has such a tricky role to be all of these and none of these sometimes in the same scene. Oldman somehow manages it all while being one Oswald at the same time.
Oldman is amazing the way he does just about everything he can with the role despite the extreme limitations of it. A one point he can be the devoted communist who is ready to defend his belief, the next he can seem like a devoted husband and Kennedy supporter even. Oldman shows Oswald believable as both a family man, but as well an abusive cold one in quick succession. Oldman does it all with the utmost efficiency. His best scenes have to be when he reacts Oswald's journey during the Kennedy assassination. Oldman runs the gambit brilliantly as both the assassin trying to get his kill, but as well the other scenario where he is the man who has just learned that he has been set up. Despite being just about silent Oldman conveys the sudden paranoia and nervousness as Oswald tries to avoid being caught.
Oldman is perfect in this role and gives what I think is the best performance in a film that is filled with strong performances. Oldman maybe goes even further than Oliver Stone wanted with his portrayal as he actually never leaves it as just one way as Oswald. He allows us to find Oswald an very intriguing character that we can almost even sorry for at times, while never saying exactly one way or another who he really is. Although by the end of the film we never do learn exactly who he is, and even though Oldman never has a full scene to himself he some how makes his portrayal of the man completely satisfying. He finds just the perfect way to take on the strange man to never completely compromise the assassin, but nor does he exonerate him. This simply is just amazing minimalist performance by Gary Oldman that made me wish he had portrayed Oswald in a dedicated character study.