That poll is not believable. For instance Coakley and Brown both had positive approval in the high 50′s in rasmussen’s poll. Coakley is not under 40%.
This sounds like a junk poll, I would say the race can go either way depending on turnout. I lived in Ma for years and they would never favor a republican by 15%.
This poll could harm Brown and make his voters complacent, assume we are tied.