In a party-line vote, Senate Democrats were unable to break the Republican filibuster of the Disclose Act, which would have required the biggest contributors to identify themselves. The bill, which had already passed the House, will probably be revived later this year, but not in time to affect the Congressional campaigns — for which the big checkbooks are now being readied.

The business community, led by the United States Chamber of Commerce, claimed the bill would “shred” the Constitution by imposing onerous restrictions on businesses. Republicans insisted on the Senate floor that the bill was blatantly designed to improve the chances of Democrats in the fall election, citing as one example a provision that allows donations of less than $600 to remain anonymous, while requiring disclosure of the rest.

Corporations are more likely to make larger donations, they said, while union members and their smaller donations are protected from disclosure. Of course, one of the founding principles of campaign finance reform is to encourage large numbers of small donations from donors of all kinds, while reducing the influence of wealth. This is not an ideological proposition; it is fundamental to ensuring a fairer political process.

Supporters of the Disclose Act did not help their case by adding several extraneous provisions that gave Republicans additional excuses for voting no. In a bill that was supposed to be about disclosure, there was no need to prohibit independent expenditures by some government contractors, or recipients of Troubled Asset Relief Program funds, or oil drillers. The House inserted an especially distasteful provision that exempted the National Rifle Association from disclosure requirements.

These provisions could have been stripped from the bill through the amendment process if the Republicans had allowed it to proceed. They can still be removed when the bill comes back to the Senate this fall. But by blocking the bill on Tuesday, opponents made clear that their real problem was disclosure itself. They want the right to poison the political atmosphere without being held accountable for their speech. During the coming onslaught, Tuesday’s vote will be worth remembering.