Fred MacMurray did not receive an Oscar nomination for portraying Jeff D. Sheldrake in The Apartment.
Perhaps what really hurt MacMurray though was that what he was good at was too problematic. MacMurray in most of his less famous roles portrayed usually kindly likable fellows, here and his other darker turns he does not entirely refute his other performance even though he is playing despicable characters. MacMurray even in this role as the amoral womanizing insurance executive still has the same sort of Fred MacMurray charm, yet he brilliantly redirects here to show it being used to troubling end. Although Sheldrake is a very reprehensible sort, MacMurray portrays the part through the film showing that he either does not care or is not aware how bad of a person he is.
Fred MacMurray carries the part excellently as he makes the command of Sheldrake entirely believable in both the business sense and the personal sense. In the business sense Sheldrake pushes everyone around in the office apparently, and gets his way doing so. MacMurray with his sly grin, and his casual but no nonsense approach fully controls the scenes he is in during the early parts of the film. MacMurray equally is effective in his scenes with Shirley MacLaine. He makes the affair believable because again there is a certain charm in his performance and even a dominance in his performance that makes it so the affair can actually be believed.
Sheldrake is a constant in the film though in that he never changes really in tone, or even in his own sense of morality. When he does something that hurts someone else MacMurray portrays as only interested to a point of pure selfishness. Even when his actions hurt himself there is no change portrayed by MacMurray, but MacMurray entirely earns the lack of change. MacMurray is steadfast in making Sheldrake the unrepentant selfish jerk he should be. There is nothing learned, when something does go wrong MacMurray portrays it as only an internal annoyance for Sheldrake, that he only really cares about how it harms him. MacMurray plays the part straight and works just as it should for the part, and the film as a whole.