Two years ago, Congress came within a single Republican vote in the Senate of following the Supreme Court’s advice to require broad disclosure of campaign finance donors. The justices wanted voters to be able to decide for themselves “whether elected officials are ‘in the pocket’ of so-called moneyed interests.”

The court advised such disclosure in its otherwise disastrous Citizens United decision in 2010, which loosed a new wave of unlimited spending on political campaigns. The decision’s anticorruption prescription has grown even more compelling as hundreds of millions of dollars in disguise have flooded the 2012 campaigns — a great deal of it washed through organizations that are set up for the particular purpose of hiding the names of the writers of enormous checks.

The ability to follow the money has never been this important since the bagman days of the Watergate scandal. But when the Democratic Senate majority made a fresh attempt to enact a disclosure bill on Monday, the measure was immediately filibustered to death by Republicans, like other versions.

Still, the vote was a chance for the public to see who stands for and against such basic transparency in political spending. The answer: not one Republican showed the courage to break ranks and speak up for disclosure.