Faced with united Republican opposition, the Senate again failed to advance a proposal Thursday that would have required corporations to more fully disclose political donations.
The vote against invoking cloture was the second failed attempt by the Senate to take up the so-called Disclose Act, written in response to the Supreme Court ruling that allowed unions and corporations to spend unlimited funds on political activities. The House passed a similar bill in June.
The legislation would require disclosure by donors supporting campaign advertising, and require sponsors to personally approve TV ads, as candidates are required to do.
Republicans criticized the measure, saying Democrats were trying to "rig the system" to their advantage.
Democrats argue the legislation would provide needed transparency. President Obama repeatedly has criticized the Supreme Court's decision to strike down prohibitions on such spending in the case Citizens United vs. the Federal Elections Commission.
In a statement, Obama called the Senate outcome "a victory for special interests and U.S. corporations — including foreign-controlled ones — who are now allowed to spend unlimited money to fill our airwaves, mailboxes and phone lines right up until election day."
Independent spending has dramatically increased on the 2010 midterm campaign, favoring the GOP.