Senate Democrats on Monday blasted their Republican colleagues for voting against the DISCLOSE Act and plan to give speeches late into the night during a "midnight vigil."

“Democrats sought to require large political donors to disclose their identities so voters could judge their motivations for themselves," Senate Majority Leader Harry Reid said. "This wasn’t a new concept. In fact, many Republicans who blocked this bill today once supported it. But today those same Republicans chose to side with powerful, anonymous donors, who like their nominee Mitt Romney appear to believe they get to play by their own set of rules."

“Judging by Republicans’ vote today and Governor Romney’s refusal to release more tax returns, Republicans have clearly decided that secrecy is more important to them than being straight with the American people,” he added.

The DISCLOSE Act would prevent outside campaign groups from hiding their donors. The bill would require organizations that spend $10,000 or more during an election cycle to file a report with the Federal Election Commission within 24 hours and identify any donors who gave $10,000 or more.

It would also require the head of any organization that puts out a political ad on TV or radio to publicly state that he or she approves the message, similar to what candidates must do now.

The legislation would prevent partisan “social welfare” organizations like Karl Rove’s Crossroads GPS from being able to hide wealthy donors. The IRS requires that nonprofit “social welfare” organizations “operate primarily to further the common good.” The organizations are prohibited from running ads in support of or opposition to candidates for public office. But groups like Crossroads GPS have attempted to circumvent the ban on partisan activities by attacking Democratic candidates in ads without explicitly urging people to vote against them.

The DISCLOSE Act was killed in a 51 to 44 party-line vote on a procedural motion. The bill needed at least 60 votes to move forward.

Republicans said the legislation was an attempt to intimidate wealthy donors and an attack on free speech rights.

“As a result of this legislation, advocacy groups ranging from the NAACP to the Sierra Club to the Chamber of Commerce — all of whom already disclose their donors to the IRS — would now be forced to subject their members to public intimidation and harassment,” Senate Minority Leader Mitch McConnell (R-KY) said.

Democrats hope to force a second vote on the bill on Tuesday.

“We recognize that you don’t win every fight in round one, and this is a fight worth continuing,” Sen. Sheldon Whitehouse (D-RI), the lead sponsor of the DISCLOSE Act.

“Putting an end to secret election spending by special interests is an essential step in protecting middle class priorities. For that reason, we are committed to continuing the debate on the DISCLOSE Act late into the night and asking for a second vote tomorrow if need be. We can’t let the special interests off the hook after just one round.”