You can still argue that Coakley is favored -- and I might even believe you. Hell, I might even wind up making that argument myself. But at this point, you can't really cite the public polling as a data point in favor of your argument.
Yglesias notes that a Republican winning in Massachusetts is hardly unheard of:
At the end of the day, it’s hardly impossible for a Republican to win statewide in Massachusetts. Mitt Romney won in 2002. Paul Cellucci won in 1998. And William Weld won in 1990 and 1994. What’s more, Weld almost beat John Kerry in 1996. There hasn’t been an open Senate seat in Massachusetts in forever, and it’s hard to beat incumbents who aren’t hit by scandal or something, but in the more open fields of gubernatorial politics the Bay State Republicans have done quite well. But the formula for winning as a Republican in Massachusetts is pretty clearyou want to be independent from the machine, and generally for lower taxes and less regulation than your Democratic opponent, but also decidedly not as right-wing as the kind of guys the GOP runs for Senate in Alabama.
But Matt still thinks Brown will lose because he's only "putting a slightly moderate spin on orthodox conservative views." Weigel is less sure:
All Republican guns are blazing, but that doesn’t translate to a ground game that can compete with the union and machine ground game that Democrats are mustering. It’s Republican activists in states like Texas manning the phones for GOTV calls. Nonetheless, there’s a growing sense that Coakley, by failing to campaign hard and define the race (and Brown) in December, might have created a GOP opening that’s impossible to close.
Blumenthal's latest thoughts are here.