Fred MacMurray did not receive an Oscar nomination for portraying Lieutenant Tom Keefer the communications officer in The Caine Mutiny.
MacMurray though excels with the character of Tom Keefer a man who is only in the navy in the moment and seems far more interested in writing his novel than really doing a proper job on his ship. MacMurray is excellent because his naturally warm presence makes it so you really do not suspect that Keefer is nearly as lowly as one might think. He cynical behavior never really comes off as one would imagine, and he really manages to make the character of Keefer work through his distinctly Fred MacMurray manner.
Keefer role in the film ends up being the one who lays the seeds in his fellow officers mind that the Caine's new Captain Queeg (Humphrey Bogart) is mentally unstable. MacMurray is really perfect in the role because although his character is devious from the start of Queeg's command, MacMurray shows it his eyes, but not in his way. When he tries to convince his other officers of the Captain's problems MacMurray is entirely convincing that he could sway them due to his charm that absolutely works for the character of Keefer.
When his true colors come out near the end of the film MacMurray is very good because he doesn't compromise the rest of his performance. In the moment where he even admits his pitiful actions, MacMurray is good in that he portrays the fact that Keefer still never seems to feel that much shame. MacMurray instead stays true to his self indulgent character who only really feels shame for the fact that he ended up being caught on his behavior. This is a good performance from MacMurray that succeeds in portraying well the tricky character of Keefer who needed to be a villain without ever seeming one.
Van Johnson who bears his very real scars in the film, which he usually covered up with makeup, realizes the character of Maryk beautifully. Johnson plays Maryk as a friendly officer who genuinely enjoys doing his duties on the ship, but as well takes his job with the appropriate seriousness. Johnson is pretty much the exact opposite of MacMurray's portrayal. Where MacMurray's portrayal was really one of underhanded cynicism, Johnson on the other hand is one of openness and honesty. He makes the positive aspects of his character of truthful, and easily makes Maryk the most likable character in the film.
When Queeg comes on board Johnson is very good because unlike MacMurray there is not a hidden hostility portrayed, but instead a genuine concern for Queeg's methods. There is nothing false about Johnson's portrayal of Maryk caring for his men, as well as running the ship in a way that works, he makes his problems with Queeg's methods ones of true concern opposed to Keefer's far petty problems with Queeg. Johnson is already very good but his performance only becomes better when Keefer starts to push the issue of Queeg's mental instability. Johnson's portrayal of Maryk's struggle with the issue as a highlight of the film.
Van Johnson is very effective in portraying Maryk's approach to dealing with Queeg's problems as well as Keefer's persistence. He keeps Maryk as a man who is very much still devoted to the Naval code, and method as evidence by the scenes where he stops the extreme mocking of Queeg. Johnson is moving because he portrays well the strong persistent beliefs in the naval tradition and does well in showing the degree of disgust Maryk feels of the other men's over zealousness in dismissing Queeg. He as well though does properly convey the internal feelings of doubt in his mind over Queeg's performance.
It is Johnson who delivers on the central conflict of the film which is to break naval protocol and mutiny to save the ship. It is Johnson's ability to give weight to the conflict within Maryk own mind that makes us sympathize with him with the mutiny, and importantly we stay with Maryk through the court martial. Johnson makes us very concerned for Maryk because he only ever showed genuine concern on the ship. Johnson creates the most powerful moments of the film during the court material through his moving heart wrenching reactions to some of the testimony that could put him at the end of a rope. Van Johnson basically saves the film giving a performance that makes me honestly wish Maryk had been the lead of the film. Johnson simply gives the best performance of the cast, and salvages as much of the film as he can with his portrayal of Lieutenant Steve Maryk.