The national mood was strongly anti-Republican. Yes, it's possible to win an election without the South, but it's certainly easier to win an election with it than without it. This is even moreso the case for the Democrats.
Obama got about 6.5% more than McCain. If we gave the Republicans a similar swing in 2004, the map would look like:
(based on a -3.5% swing against Kerry and a 3.5% swing to Bush - although I'm too lazy to tamper with margins in states Bush actually did win).
This article's comments about the Democrats not needing the south are about as accurate as looking at that map and saying that Ohio is no longer relevant on the race because the Republicans could have lost it and still won.
The combination of states AL, AR, GA, KY, LA, MS, SC and WV = 77 ECVs.
A democrat winning CA and NY has easily compensates by gaining 86 ECVs right there. Even CA with the lesser IL still yields just one short of that combination of states - 76.
I'm rambling because I'm tired, but what I'm trying to say is that while it is technically true that Democrats (and theoretically Republicans, although it's harder for them) can win without the South, it certainly makes it a lot easier. Obama didn't win despite losing the south, he won because he picked up CO, OH, NM, NV and FL - the real swing states, plus NH, MI, PA - the somewhat swing states, and then went further to win NC, VA and IN - states that the democrats haven't won in quite a while. If he hadn't gained those states, it would have been quite difficult for him to win without the states. Yes, there are winning combinations for the Democrats that don't include southern states, but they're fewer than the winning combinations that include them.
Oh, and once again, sorry if I was rambling a bit too much and didn't make a lot of sense. I can try redoing this tomorrow if it helps
