Despite promises of Senate Democrats to amend their signature campaign disclosure legislation, a unified Republican caucus today again blocked the legislation from an up-or-down vote in Congress' upper chamber.

Republicans stuck together to oppose theDISCLOSE Act, a legislative response to the Supreme Court's January ruling in Citizens United v. Federal Election Commission, which opened the door for unrestricted sums of corporate and union treasury money to fund political advertisements. A unified Democratic caucus supported the legislation, voting 59-39 on a procedural vote that needed 60 votes to pass.

Republicans successfully filibustered the DISCLOSE Act in July as well, after the Housenarrowly passed the bill in June.

The bill's main focus is new reporting and disclosure requirements for groups that run independent expenditures, such as television ads that overtly advocate for or against federal candidates, and electioneering communications -- that is, broadcast communications that feature a federal candidate but don't expressly advocate for that candidate's election or defeat. 

New restrictions would apply to corporations, unions, trade associations, so-called 527 groups and 501(c)(4), (c)(5) and (c)(6) advocacy organizations. 

One provision would require groups to show the names of the top donors in the advertisements and have the head of the organization or the group's largest contributor "stand by the ad" -- giving the same, familiar disclaimer that candidates must include in their advertisements: "My name is so-and-so, and I approve this message."

Additionally, the bill would prohibit companies from producing independent expenditures if they met certain criteria. These include bailout recipients with outstanding loans from the government's Troubled Asset Relief Program (TARP), large government contractors and foreign-controlled companies.

Senate Democrats acquiesced to some of the chief Republican criticisms of the DISCLOSE Act and promised to keep the new regulations from going into effect until January, after the contentious 2010 midterm elections are over. They also offered to scale down the bill to its core disclosure requirements.

"We do not want to chill speech," Sen. Charles Schumer (D-N.Y.), the bill's lead sponsor in the Senate, said on the floor before the vote. "We merely want the American public to have details about who is speaking."

Nevertheless, moderate Republicans such as Sens. Susan Collins (R-Maine), Olympia Snowe (R-Maine) and Scott Brown (R-Mass.) -- who reform advocates had targeted -- stood behind Senate Minority Leader Mitch McConnell (R-Ky.), who is a long-time opponent of campaign finance regulation. 

On the Senate floor today, McConnell blasted the legislation and its Democratic supporters, saying, "They want government to pick and choose who gets to speak in elections, and how much they speak."

After the vote, President Barack Obama, who supports the legislation, criticized Senate Republicans.

"I am deeply disappointed by the unanimous Republican blockade in the Senate of the DISCLOSE Act, a critical piece of legislation that would control the flood of special interest money into our elections," Obama said in a statement. "Today's decision by a partisan minority to block this legislation is 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. And it comes at the expense of the American people, who no longer have the right to know who is financing these ads."    Dozens of new organizations have taken advantage of the loosened rules for political spending. Top liberal and conservative political operatives have registered new "super PACs" or "independent expenditure-only committees" with the FEC, as OpenSecrets Bloghas previously reported.

Money has also flowed into 501(c)4 outfits, which are not required to disclose any information about their donors, and which, by definition, are not allowed to be primarily focused on politics. These 501(c)4 groups have nonetheless spend tens of millions of dollars so far this year on overt political ads.

You can find more information about "super PACs" in the recently launched independent expenditure database on OpenSecrets.org. You can also find more reports here fromOpenSecrets Blog about these new groups and the fallout from Citizens United and other federal court rulings on campaign finance, including SpeechNow.org v. Federal Election Commission.