One nugget from Pew Research that I'd missed earlier: Barack Obama performed 9 points better than John Kerry among urban whites. This was not by any means the most important factor in his election, but it helps to explain the large improvements that the Democratic ticket made in states like Colorado and Nevada, where a great deal of the population is concentrated in Denver and Las Vegas, respectively, and why Republicans were at best able to tread water by targeting the rural areas of Pennsylvania, while Obama waltzed his way to winning large majorities of white and black voters in Philadelphia.
This also attests, of course, to the stupidity of bashing big cities. Roughly 82 million Americans live in cities of 100,000 persons or more, including 40 million in cities of 500,000 persons or more. This does not count smaller cities or suburban areas, which account for another 150 million Americans or so. (Don't neglect the fact, also, that many Americans who do have their residence in big cities may nevertheless work or play in them, and therefore think well of them). By contrast, only about 60 million Americans live in rural areas.
The Bush-Rove team of 2000 and 2004 understood the importance of appealing to suburban voters ... that is a viable strategy. Pitching your appeal to rural voters, on the other hand, probably will not work. They're outnumbered by the city dwellers in the first place, and if your attacks are strident enough that the suburbanites start to side with the urbanites, you've given yourself a big problem.