There seems to be a misconception out there that Bush = Southern Conservativism in US politics, but just take a look at the list of Bush's best states (in winning percentage) in 2004:

Utah 72.7%
Wyoming 69%
Idaho 68.4%
Nebraska 66%
Oklahoma 65.6%
North Dakota 62.9%
Alabama 62.5%
Kansas 62%
Texas 61.1%
Alaska 61.1%
South Dakota 59.9%
Indiana 59.9%

On this list, only Alabama is "southern", (Texas is often considered more a "western cowboy" state) All the others are western or northern, mainly rural states. They all have very few low income blacks. By way of contrast Bush was able to win most southern states "only" in the mid 50 percent range.

In historic terms, Bush won by getting the same groups of voters that Nixon and Ford (both called "moderates" today) got back in the 1970s: suburban and rural white middle and upper class votes. The big difference then and now is that as older southern whites who still remembered the Civil War (from their fathers' and grandfathers' generation) died off, their children stopped voting for conservative (often racist) democrats, and now vote republican just like most non-urban northern whites.

At the same time, northern democrats are able to organize massive black votes in the northern inner cities. With 80-90%+ turnout, they come out of the cities with too big a lead for any republican to catch.

Here is the list of Democrat Kerry's best states:

District of Columbia 89.2%
Massachusetts 62%
Rhode Island 59.4%
Vermont 58.9%
New York 58.4%
Maryland 56%
Connecticut 54.3%
California 54.3%
Illinois 54.8%
Hawaii 54%
Maine 53.6%

With a few exceptions (Vermont and Maine), they are all urbanized states with very high black or other minority (mainly hispanics and jews) population, these groups provide the margin for Kerry's victory in nearly all his winning states.