I think some substantial portions of this post from Tyler Cowen are off-base, but point six I think is correct:
There is a reason why the Democratic establishment does not, as Matt Yglesias so often recommends, abolish the 60+ requirement. Often they prefer inaction, combined with the ability to blame the Republicans for such. See #4. The often-sad truth is that the Democrats as a whole prefer to tailor policy to pander to their “worst” members.
I don’t think you need to appeal to the idea that people prefer to pander to the caucus’ worst instincts so much as simply the fact that legislators prefer to do nothing at all. The supermajority — and, more broadly, the extreme difficulty of moving legislation — makes it easier for elected officials to make contradictory commitments to various people. Consider that as long as Democrats clearly didn’t have the votes to pass the Employee Free Choice Act, they could promise labor law reform to unions while also reassuring business that no such law was going pass. After the election suddenly there were sixty members who’d promised to vote for EFCA, which created an awkward situation for those members who, in fact, preferred to do what business wanted and killed it. They had to flip-flop in a not-very-pretty way and anger a lot of people. If it took 67 votes to move a bill, they would have been in much better shape, loyal friends to Wal-Mart and the AFL-CIO alike.
This kind of thing is why I think it’s important to pay more attention to institutional and process issues than most people do. We’ll never elect a legislature of angels, but people’s incentives and desires can play out in better or worse ways according to the context.