Aaron Eckhart did not receive an Oscar nomination for portraying Harvey "Two-Face" Dent in The Dark Knight.
Eckhart takes on the role in a suave charming approach to the part. Harvey Dent really is the ideal politician who actually believes what he stands for, and is the man his face seems to say that he is. He is not just a hallow shell in the suit, and Eckhart effectively carries himself as an official who honestly does care. There is a hint of his passion for his job being any sort of facade. His portrayal of the goodness in Dent is entirely natural, and never seems forced in the least.
Like Gary Oldman as Gordon, Eckhart is able to bring to life the inherit strengths of Dent's character. Eckhart gives a fairly controlled performance the emphasizes that Dent has, or least believes that he has everything all together. Despite the problems that seem to present himself constantly, including death threats, Eckhart portrays Dent as having a inherit drive, and calmness that shows that although Dent is aware of the problems around him he always does his best to take it in stride. He has a power and passion within his performance that expresses well his good intent.
Harvey Dent does not keep his calm and cool reserve through the film though importantly there are relatively small moments that Eckhart puts into his performance that indicate the eventual path his character will go. These moments really are not really all that negative but rather show small little kinks in his white armor. Of course these are only moments of frustration that Eckhart does bring out convincingly as part of Dent, and making it so that Dent really is of course humans flaws and all.
As the film proceeds and the Joker's reign of terror comes very close to home for Dent, there is a much darker side shown by Eckhart as he interrogates one of Joker's men. Eckhart brings out a great intensity in this scene that is very brutal. Important to this scene though is that Eckhart brings it in with the calmer Dent of before. Eckhart does not plays the intensity here as something that comes from his stressed emotional state, far more than any sort of insanity. Again though Eckhart again alludes to more flaws within Dent efficiently without comprising the beginning of his performance.
Of course the whole Harvey Dent character is changed completely after half of his face is burned off, and his fiancee is killed by the Joker. His change into Two-Face is of course instant as it is caused by a sudden act of violence. Eckhart actually manages to earn the change by having the appropriate hints early on as well as having a bit of transition just after the accident. In his first post change scene Eckhart is excellent in portraying the weight of trauma on Harvey as he becomes a bitter man, and the goodness of him replaced with only with anger fueled by his pain.
Eckhart is excellent in his moment with Oldman, as he portrays a complete lack of hope losing all of the passion shown at the beginning. He transforms ever lower after an "inspirational" talk from the Joker. Eckhart makes this transformation work as well though as it is not that Joker turns him evil from his talk, but rather just allows him to focus his anger into a path of vengeance. Eckhart is very strong in his moments toward the end of the film as Dent moves forward in his path of revenge only stopping to flip a coin to determine the fate of his victims.
His scenes at the end show not a villain like Ledger as the flamboyant Joker, but instead a deranged man who has no higher plan past his 50/50 judgment. Eckhart is very striking in the end showing the psychotic derangement of Harvey at the end that is only filled by his hatred, but importantly he always has the underlying sadness in his performance exemplifying the fact that it all comes from his loss. It is powerfully chilling end to his path as Harvey, as he marvelously realizes his character's entire decay down to his lowest end. I would not quite put his performance quite up there with Ledger and Oldman, but on his own he creates his character's journey effectively and gives a strong performance throughout the film.