More from that same article in The Guardian,

Remember that in 2004 every American city with a population over 500,000 voted Democrat, and the Republicans won by taking the countryside and the outer suburbs. The blue state/red state division is better expressed in terms of the persistent conflicts between the big cities and their rural hinterlands, over land use, water rights and environmental, class and cultural issues. Red states are simply those where the country can outvote the urban centres, while in blue states the opposite is true.

and if the dems care about having a candidate with broad appeal….

So Obama’s victory over Clinton in rural Nevada says something important about his ability as the apostle of national reconciliation. To win against Clinton in Elko County (black population: 0.8%), he had to convert not only white Democrats, but a large number of independents and people who had voted Republican until caucus day; a feat he pulled off with dazzling facility. Any Democrat nominee who can do that, deep in Republican country, is likely to gain the presidency; and Obama has proved that he can.