Edward's Rise Explained sort of

There are three possible causes for Edward's strong showing in Wisconsin and polling elsewhere.

1) Edwards has more cross-over appeal. See William Saletan's analysis here.
2) Republicans are voting strategically to draw out the democratic primary and force the dems to spend against one another for as long as possible.
3) Edwards remains sufficiently unknown that people can still fill him with there own hopes, but Kerry has become a real person unable to be all things to all people.

There is undoubtedly some of all of this at work. Which might be a dominant cause or what the proportions might be I can't say.