The lesson of the 2012 election was to “trust the data,” especially the polls:
FiveThirtyEight and I became emblems of that narrative, even though we sometimes tried to resist it. What I think people forget is that the confidence our model expressed in Obama’s chances in 2012 was contingent upon circumstances peculiar to 2012 — namely that Obama had a much more robust position in the Electoral College than national polls implied, and that there were very few undecided voters, reducing uncertainty. The 2012 election may have superficially looked like a toss-up, but Obama was actually a reasonably clear favorite. Pretty much the opposite was true in 2016 — the more carefully one evaluated the polls, the more uncertain the outcome of the Electoral College appeared. The real lesson of 2012 wasn’t “always trust the polls” so much as “be rigorous in your evaluation of the polls, because your superficial impression of them can be misleading.”