The perception among independents in Mass. would be that Romney is more conservative than they would like. It’s not a matter of what you believe, it’s how Brown would have seen it playing out.
But it wasn’t just Romney. There were many conservatives who expressed support for Brown, but he wasn’t getting endorsements from them, or having them campaign or speak publicly with him. And it wasn’t just conservatives, Brown didn’t want the RNC or other outside groups in general showing up for him.
So my point really is that Brown kept a lot of people at arm’s length during the general election, not that he kept Romney out because Romney was conservative.