2012 Election County-By-County:
What did Romney's defeat really look like? Forget the traditional post-election maps colored red or blue county-by-county. In most states the colors cover empty space. It's population weights that tell the real story. And so here is a heat map with the size of states in the redness or blueness, weighted by their relative population.
Update: The Washington Post has a chart showing the break toward Obama or toward Romney among various voters' categories, compared to 2008. Only one age group broke more to Obama this year than then, ages 30-44. Every other age group, including youth, broke right.
The chart shows that overwhelmingly, the electorate (by categories) this year broke right, including ideology, marital status and even some ethnicities.
And Obama was still elected despite garnering something like 8 million fewer votes than in 2008. (IIRC, this makes him the first incumbent ever to be relected to a second term with fewer votes than his first term.)
The conclusion is obvious: not enough voters defected from Obama to put Romney over the top. The chart even shows that in the way it presents the data, for example this section:
Yes, women broke to Romney. So did young voters. But the majority of them still supported Obama. This repeats down the chart. All this means, I think, that Romney was defeated more by people who didn't vote at all than by those who voted for his opponent. That’s why I think a heat map that somehow displays relative weights of nonvoters in red or blue areas would be a useful analysis.
This seems to track with what I say above: