A modest but worthwhile effort to curb the power of money in politics died on Tuesday afternoon when Senate Republicans refused to let debate on the measure go forward.

The DISCLOSE Act would require corporations and interest groups to identify themselves when they sponsor political ads and, in the case of smaller organizations, to reveal their donors.

President Obama and Democratic leaders hoped the bill would, among other things, help undo the damage of the recent Citizens United ruling, in which the Supreme Court threw out limits on corporate political spending. And since the bill merely called to publicize who was putting money into politics, rather than limit that money, Obama and the Democrats hoped they could peel off enough Republican votes to break a filibuster. They were wrong. Not one Republican voted to proceed with debate--not even after the Democrats modified the bill, in order to address GOP arguments that it would treat unions differently from other groups.

This would be a fine moment to ponder, once again, the way the filibuster thwarts democracy. Fifty-seven of the Senate’s one hundred members think the bill should pass, but they can’t act because a minority of senators has the power to thwart action.

But the real story today is the hypocrisy of what used to be the Republican Party’s moderate, sensible wing.

Scott Brown campaigned for office on a platform of more transparency in government. In 2001, Susan Collins and Olympia Snowe voted for the McCain-Feingold bill, which was far more restrictive. None of them voted to let the debate go forward.

And then there is John McCain himself. A decade ago, McCain did more than put his name on a major piece of campaign finance legislation. He made the fight against money in politics a personal crusade, energizing supporters with statements like this one he made during a Virginia speech:

I have called for the reform of campaign finance practices that have sacrificed our principles to the demands of big money special interests. I have spoken against ... [APPLAUSE] ... I have spoken against forces that have turned politics into a battle of bucks instead of a battle of ideas, and for that, my friends, and for that, my friends, I have been accused of disloyalty to my party.

Nobody is accusing McCain of that anymore. 

Update: More dormant than dead? My old colleague Jesse Zwick reports in the Washington Independent that the bill's advocates hope to make another run at passing the measure in September.