Not just for Wisconsin, but also for Super Tuesday.
Edwards: Obviously if he is going to win the nomination, he needs to start winning primaries. For the start of the "two way race" between him and Kerry, I think anything beyond 45% (leaving out Kucinich and Sharpton and uncomitted: i.e losing to Kerry by less than 55-45%) would be a show of momentum for him and allow him to continue.
Kerry: If he can keep beat Edwards 3-2 or better (60-40%), he would show that he is the chosen nominee by Democrats and put and end to the race.
The no man lands, and the worse case scenario for both candidates is Kerry getting between 55-60%. It would show a lot of weakness for Kerry, but at the same time, not show enough strength for Edwards to be able to seriously challenge Kerry.