Among the Republicans voting Tuesday to block a bill requiring disclosure of donors underwriting political ads were many who have benefited from the contributions of groups that don't disclose their donors.

Seven GOP senators who benefited from close to $1 million in dark money during the 2010 campaign all voted against the DISCLOSE bill. Here is a list of them, along with the amount of dark money spent to help their campaigns:

• Sen. Kelly Ayotte, R-N.H.: $3.7 million
• Sen. Roy Blunt, R-Mo.: $2.9 million
• Sen. Marco Rubio, R-Fla.: $2.7 million
• Sen. Ron Johnson, R-Wis.: $2.6 million
• Sen. Rand Paul, R-Ky.: $1.8 million
• Sen. Scott Brown, R-Mass.: $1.5 million
• Sen. John Boozman, R-Ark.: $925,000

Sen. Mark Kirk, R-Ill., who saw $6.9 million in dark money spent on his behalf two years ago, did not vote. He is on medical leave recovering from a stroke. Keep in mind that many of these Republican senators also faced attacks by outside groups that may have had them nervous. However, the hidden money, in each of their races, was dominated by pro-Republican groups.  

These numbers were totaled using data from the Center for Responsive Politics and represent what outside groups not disclosing donors — usually 501c4 nonprofit groups — spent in the senators' races in 2010 — either favoring the Republicans or attacking their opponents.

They likely understate the amount of dark money in those races, as they represent only the expenditures that were disclosed to the Federal Election Commission: The FEC requires spending reports for any activity that explicity calls for the vote or defeat of a candidate (known as independent expenditures). That leaves many so-called "issue ads" — which are overtly political but stop short of advocating for a candidate's election or defeat — off the radar screen. Spending on those ads doesn't have to be reported unless they air within 30 days of a primary or 60 days of a general election.

The only two sitting Republican senators in close reelection races this November — Sens. Scott Brown of Massachusetts and Dean Heller of Nevada — have already seen dark money flowing into their states on their behalf. So did Sen. Orrin Hatch, R-Utah. Sunlight's Follow the Unlimited Money Tracker shows Hatch benefited from at least $300,000 in dark money in his challenging primary race. This $300,000 was not from super PACs or traditional PACS, which have to disclose their donors, but rather from nonprofit groups or corporations that do not have to register with the FEC. Hatch was also the beneficiary of two ad campaigns–one promoting him and one attacking his opponent — by the 501(c)4 group American Action Network. Because of its nonprofit status and the timing and nature of its ads, AAN disclosed neither its donors nor the amount it spent on the ads.

Heller and Brown, both in tossup races, according to nonpartisan political handicapper Charlie Cook, have seen benefits too.  The same day that the Senate voted down DISCLOSE, the Chamber of Commerce launched an ad criticizing Heller's opponent, Rep. Shelley Berkley. Crossroads GPS, the shadowy group that says it will spend $300 million on the 2012 election along with its sister group, hit Berkley with an ad in April.

Crossroads GPS has also run multiple ads against Brown's opponent, Elizabeth Warren. And the Chamber has vowed to play in that race too.