Obama defining himself as Lincoln would redefine the civil war as the conservatives are the Confederates who need to be not only defeated, but vanquished.
That was Spielberg's intent in the movie "Lincoln". It was a subliminal analogue for Obama's vanquishing of the ideological Neanderthals who oppose his courageous imposition of socialism/emancipation. The fact that Lincoln was a Republican merely served to make the director's motivation less obvious, giving it some cover.