Boris Shor in January:
the pivotal Senator will now be a Republican, not a Democrat . . . Brown stands to become the pivotal member of the Senate.
The New York Times today:
The Senate voted on Thursday afternoon to close debate on a far-reaching financial regulatory bill . . . In an interesting twist, the decisive vote was supplied by Senator Scott Brown, the Republican freshman of Massachusetts . . .
I don't think this story quite fits Shor's thesis (although generally I agree with Shor's point). Snowe and Collins were already on board, the difference from yesterday was Specter, Brown, and Reid. Cantwell and Feingold were still voting against cloture and I don't think you can plausibly argue that Brown is to the left of Cantwell and Feingold.
"I don't think you can plausibly argue that Brown is to the left of Cantwell and Feingold."
I don't think you can, either. This sounds like classic back-room dealmaking; Brown gets to be principled, in a supportive district, and Cantwell and Feingold get to maintain their "street cred" among conservatives. Win-win.