The easiest answer to the question of why Scott Walker won is because he got more votes than Tom Barrett.
Of course, how he did that is entirely another matter. There are a lot of theories floating around, but for now I’ll go with that and let the pundits fall where they may.
In fairness, I think Josh Marshall does a concise job of summarizing what it all means. So does Greg Sargent. Between the two of them, you have a pretty level-headed assessment of what this election bodes — and doesn’t — for November.