Would we agree that you need a decent Republican environment for a Republican to win, with some comfortable upper middle class people turning their backs on the Dems? If so, that means lots of wealthy moderates in Needham, Newton, and Brookline who otherwise vote Democratic, voting for a Republican they consider safe. The Republican doesn't have to win that part of the district or come close, but he needs a) to get some votes there and, more importantly, b) not anger people so much that they come out in force against him.
You need a Mitt Romney or a Scott Brown, not someone who unabashedly plays wedge issues.
Obviously, for the GOP to pick up the seat, they need someone who can win over Democrats. But in Massachusetts, the Democrats who do turn their backs and vote for Republicans are not the wealthy moderates in Brookline you're describing. They're solid, urban Democrats. Largely immovable.
When I've looked at in-depth polling as part of Mass GOP campaigns, the only lean-Dem voters that the GOP has a shot of moving are the more conservative, blue collar ones in towns like Taunton. Picking Richard Ross over Hodgson might get the GOP an extra 5,000 votes total in Brookline, Newton, and Wellesley. At the same time, though, I'd expect Hodgson to be able to make those 5,000 votes up in Bristol.
By the numbers, I really do think Hodgson v. Pacheco is a better shot for the GOP than Ross v. Pacheco, even if Ross performs better north of Bristol.
