A month ago, I predicted, on the basis of his state legislative record, that newly-elected Senator Scott Brown (R-MA) would join the liberal wing of Senate Republicans. A few days ago, Brown joined Republicans Olympia Snowe, (ME), Susan Collins (ME) and George Voinovich (OH) in shutting down a threatened Republican filibuster of a $15 billion Democratic stimulus bill. And just now, that bill was passed.

Some of the conservative reaction has been of resigned sighs, but others were more outraged. But re-election as a Republican in Massachusetts isn’t going to be easy in 2012, even with a massive war chest. Expect more of these votes.

Political science is mostly about explanation, not prediction. But I couldn’t help myself on this one. Of course, it’s just one vote. We await more votes to see where he really lines up relative to his new colleagues. And his campaign rhetoric (and ideology) will make it very difficult for him to vote for the Senate (or Obama’s) version of health care reform.

Update 2/25: That was fast. Hours after my post, Stanford’s Simon Jackman posts his first estimate of Brown’s ideal point. And, lo and behold, he’s the leftmost Republican, as per my prediction. Of course, with so few votes, it’s a necessarily noisy estimate. Here it is:


The dots are the best estimate, and the lines are the uncertainty around that estimate. So Brown could be as conservative as Lisa Murkowski (R-AK), but he could also be as liberal as Robert Byrd (D-WV). Again, things will change as more votes happen, but you heard it here first.