I doubt that this race, which was once very close, has become this lopsided in a few days when virtually nothing has happened. 48-41 would be the numbers I would guess.
I think you are right, but what has happened is that the Democratic voters have come home. Granholm has been hitting Devos hard on his corporate ties and also emphasizing her own record in creating jobs, and it's helped changed the dynamics of the race.
Devos was just never a very good candidate, kind of a personification of the negative stereotype of what a Republican is in many ways. He's quite conservative and not the kind of Republican who can win in Michigan, especially in this environment.