Late breakers went for Obama in 2012 because of the Christie incident. That storm gave Obama the chance to look presidential and all of that in the face of a disaster, with a Republican slobbering all over him. Christie elected Obama in that moment.
I think your analysis is correct as far as it goes, but I base my observation on these facts:
In 2008, Obama had 69.5 million votes and won by 9.5 million. The popular vote was 58.2%
In 2012, Obama had 66 million votes and won by 3.5 million. The popular vote was 55% about the same as 2004.
From this I deduce that Sarah Palin’s presence on the ticket brought out the sort of evangelical voters who often decline to vote because of the generally unsuitable nature of both tickets, while at the same time it probably alienated a larger number of moderates. But if the stay-at-home evangelicals had voted for Romney, he might have won or at least tied Obama in the popular vote more or less. The results in the 2012 electoral college would require more study time than I have right now.