Much has been made of Scott Brown’s (R-Mass.) election to the U.S. Senate, since by taking the seat held since time immemorial by Ted Kennedy, Brown has effectively squelched congressional Democrats’ “filibuster-proof” 60-seat majority. This has been interpreted variously as rank ineptitude on the part of Brown’s Democratic opponent, former Massachusetts state Attorney General Martha Coakley, and as a “referendum on health care reform” by voters angry with Democratic inaction since they won their majority two years ago.

Lost in these analyses are the different sets of implications for any Democratic coalition in the Senate. Counterintuitively, 59 may be a more powerful majority that 60, at least from the perspective of Democratic party leadership.

Some political science geekery, if I may. The theoretical models of group bargaining all depend heavily on the concept of “veto players,” at least since Anthony Downs popularized the idea of two-dimensional “policy space.” Without getting to deeply into the arcane calculus of this framework, it’s well-established that the “veto player” — whoever in the bargaining group with de facto veto power over a proposition — and his preferences have a lot to do with the outcome of the group’s bargaining.

This is easiest to illustrate with a simple example. Imagine three people have to decide on whether to buy a new television for their apartment. They’ve decided to make the decision democratically, with a 2-1 vote in either direction determining whether or not the TV gets purchased, and all three will contribute equally if the decision is to buy the appliance. Roommate A is all for it, and Roommate B is staunchly against. This means that Roommate C is in a very powerful position, and has the opportunity to court either A or B (or both) with her prospective vote in their favor.

Democrats’ 60-vote majority in the Senate gave each individual Senator this Roommate C leverage — leverage that very few politicians are unwilling to bring to bear. Losing that magic 60th vote meant that the filibuster-proof coalition would disappear, meaning that a simple threat of a “Nay” would send party leadership scrambling to win it back. Witness, for example, the $300 million promised to Louisiana Senator Mary Landrieu in one version of the Senate’s health care reform bill, and the popular shrieking that followed suit. It may indeed look like “extortion,” but in Congress, that’s called politics.

Now, with only 59 Democrats holding Senate seats, no Democratic Senator has the ability to hold the bill hostage for special treatment. Instead of being able to look at the health care reform bill as an opportunity for specialized treatment for their districts, Democrats’ primary interest is in seeing the bill passed — it’ll be better for their party label, and make a much better talking point next time they’re up for re-election than a loss would. Sure, a filibuster is as close to inevitable as makes no difference, but filibusters are politically costly (here’s NRO’s Ramesh Ponnuru making the point in 2005, about judicial nominees) and are eventually subject to high risk of defection.

The take-home message here is that 59 is a much less-fragile number than 60 is, at least in the Senate. And it’s still well above the 50+1 mark needed to pass a bill. Expect to see Democrats bringing a much more united front to the table on health care reform and any other measures they choose to pursue in the near future.