Why did Wisconsin go so much for Obama? It blew past Minnesota and Iowa.
I think WI has more blacks than both states.
It doesn't explain the massive swing, from barely Kerry to a 13 point margin.
It could be the Chicago media market.
I don't think that really explains it either since such a small corner of the state is in the Chicago media market and Obama saw widespread gains across the entire state. I think the real reason he did so well here has to do more with the primary.
Wisconsin was part of Obama's post-Super Tuesday rout of Clinton during February. This was the height of Obama's primary campaign and they were trying to clinch the nomination by increasing their victory margins. The Obama ground game came out in full force and defeated Clinton by a massive 18 point margin. But, like in so many other states, they didn't stop there. They kept going, all the way to November.
McCain, on the other hand, never had to compete in Wisconsin during the primary. By the time it rolled around, McCain had become the assumed Republican nominee and his primary was essentially over. He didn't show up in Wisconsin until it was way too late. In fact, I think you can attribute many of Obama's success to Clinton's stubborn refusal to admit defeat. Whilst McCain was resting comfortably, Obama was organizing ground games in Nebraska, Virginia, Wisconsin, Ohio, Pennsylvania, Indiana, and North Carolina. I don't think its a mere coincidence that Obama scored major wins in these states.
In hindsight it seems that Clinton actually did Obama a huge favor. All that hand wringing about party divisiveness seems silly now. In fact, I'd say its pretty clear that Obama's success in November can be traced directly back to the Democratic primary. The fact that Obama was building a nationwide campaign organization while McCain twiddled his thumbs is one of the major reasons this became an electoral landslide instead of a strong but not overwhelming Democratic victory.