One of the things in films that really irks me is the flawless hero. Usually a casualty of the "based on a true story" film that goes through approval from the people the film is based on (or their estate), these characters are always clear-headed, constantly making the right decision to benefit everyone. They're usually given some sort of token flaw, like their dedication to their job/mission/whatever causes some strain on their personal life, but even that's typically portrayed as a necessary evil compared to their noble cause.
But it's not enough for Abraham Lincoln, one of the greatest presidents the United States has ever had, and, in 1939, when Henry Fonda played him, perhaps THE greatest, to simply be a flawless, noble man. It's not enough for him to take on a case nobody believes in (and--SPOILERS--win the case by finding a totally different killer based on the loosest of evidence). No, Abraham Lincoln has to be the greatest person who ever lived. He has to love every elderly woman as though she were her mother, fall in love with the concept of the law the first time he touches a law book, tell the funniest jokes anyone has ever heard, preside as judge of a pie-eating contest in which there are no winners, only amazing pie, win every fight before it has the chance to even start, calm down an angry mob with only the soothing sound of his voice, and be the town champion at splitting a log in half.
In this way, Ford's film slingshots around and becomes entertaining in a whole new way. Never mind the random appearances of future wife Mary Todd and future rival for the Presidency Stephen Douglas. It's one of the silliest and almost certainly the most righteous portrayals of a major historical figure I've ever seen.