Not sure why this would be. The city proper is very Democratic. Rural Wisconsin is usually pretty Republican. Milwaukee proper is a shrinking city, which may account for the suburbs having more to say in the metro numbers. What really surprises me being a former Wisconsinite is how well Gore did in extreme norther Wisconsin by Lake Superior. I hadn't realized this.
I am not surprised by Al Gore's success around the Lake Superior region. The towns and villages in and around that area tend to have economically lower class people and therefore have the tendency to vote Democratic.