The general consensus among historians among the ones who can handle the fact that 'Lincoln' is in fact historical fiction is that we demonstrate enormous fidelity to history and that beyond that we've actually contributed a line of thinking about Lincoln's presidency that's somewhat original.
The whole course of human history may depend on a change of heart in one solitary and even humble individual - for it is in the solitary mind and soul of the individual that the battle between good and evil is waged and ultimately won or lost.