The Sunlight Foundation has crunched the numbers and calculated [3] the "return on investment" that big-spending Super PACs and "dark money" groups achieved in the 2012 cycle. It reflects how much of the money spent by each group went to support candidates who won (or to oppose candidates who lost) in the general election campaign.

It may come as a surprise to some, but the group with the worst return on investment was the National Rifle Association. The biggest winner? Planned Parenthood.

Below, we reproduce a partial list of Sunlight's findings:

Biggest Losers

American Crossroads: 1.29% Return on Investment

American Crossroads [4] is a right-wing Super PAC created in 2010 by right-wing political operatives and "advised" by Karl Rove. The Super PAC spent a total of $104,710,427 in the 2012 election cycle, but only 1.29 percent of that money was spent on elections that resulted in the group's desired results.

NRA Political Victory Fund: 0.81% Return on Investment

The National Rifle Association [5] of America Political Victory Fund, the Super PAC associated with the NRA, spent a total of $11,787,523 in the 2012 election cycle. A minuscule .81 percent of that money went towards elections where the NRA's preferred candidate won.

American for Responsible Leadership: 1.96% Return on Investment

American for Responsible Leadership, "a Phoenix-based 501(c)(4) nonprofit group [6] run by an unlikely collection of Arizona Republicans," spent a total of $5,022,762 on the 2012 election cycle. Just 1.96 percent of that money backed candidates that emerged victorious.

The American Future Fund: 5.57% Return on Investment

The American Future Fund, a "dark money" 501(c)(4) which "was formed to provide Americans with a conservative and free market viewpoint," [7] spent $23,959,072 in the 2012 election cycle. Only 5.57 percent of that money went toward elections that ended with the Fund's desired results.

US Chamber of Commerce: 6.9% Return on Investment

The US Chamber of Commerce [8], the most powerful business lobbying group in the US, spent a total of $32,676,075 in the 2012 election cycle. 6.9 percent of that money backed candidates that ultimately won.

NRA Institute for Legislative Action: 10.25% Return on Investment

The National Rifle Association [5] (NRA) Institute for Legislative Action, the lobbying arm of the NRA, spent a total of $7,448,017 in the 2012 election cycle. 10.25 percent of those funds were spent on elections where the group's preferred candidates won.

Now or Never PAC: 14.3% Return on Investment

The Now or Never PAC, a Super PAC "committed to helping the Republican Party recapture the U.S. Senate," [9] spent a total of $7,760,174 in the 2012 elections cycle. 14.3 percent of that money backed successful candidates.

Crossroads GPS: 14.4% Return on Investment

Crossroads Grassroots Policy Strategies [10] (Crossroads GPS), the "dark money" 501(c)(4) sister of Karl Rove's American Crossroads, reported spending $70,710,008 on the 2012 election cycle. 14.4 percent of that money was spent on elections that ended in the group's desired results.

The Ending Spending Action Fund: 15.34% Return on Investment

The Ending Spending Action Fund, a Super PAC financed primarily by billionaire businessman Joe Ricketts, spent a total of $13,238,296 in the 2012 election cycle. 15.34 percent of that spending backed successful candidates.

FreedomWorks: 24.51% Return on Investment

FreedomWorks [11] for America, a Super PAC closely associated with the Tea Party movement that works "for less government, lower taxes, and more freedom," spent a total of $19,180,828 on the 2012 election. 24.51 percent of that money went towards elections that ended in the group's desired results.

Club for Growth Action: 41.37% Return on Investment

Club for Growth [12] Action, a Super PAC whose "sole mission is to defeat big-government politicians and to replace them with economic conservatives," spent a total of $16,585,176 in the 2012 elections cycle, much of it in the primaries. They achieved a 41.37 percent return on investment.

Patriot Majority: 42.52% Return on Investment

Patriot Majority USA is one of the few "dark money" 501(c)(4) on the Democratic side, "whose multifaceted agenda includes support for workers' rights, preserving social safety nets and reforming tax laws." [13] It spent a total of $7,509,093 in the 2012 election cycle, and 42.52 percent of that money went towards elections that ended in the group's desired results.

AFSCME PEOPLE: 44.6% Return on Investment

American Federation of State, County, & Municipal Employee's (AFSCME) PEOPLE, a Super PAC for the labor union AFSCME, spent a total of $12,694,301 in the 2012 election cycle. The group achieved a 44.6 percent return on investment.

Independence USA PAC: 45.74% Return on Investment

The Independence USA PAC is New York City Mayor Michael Bloomberg's Super PAC, formed to support "Republican, Democratic and independent candidates who support three of his biggest policy initiatives: legalizing same-sex marriage, enacting tougher gun laws and overhauling schools." [14] The group spent a total of $8,169,429 on the 2012 election cycle. 45.74 percent of that money went towards elections that ended in the group's desired results.

House Majority PAC: 46.46% Return on Investment

The House Majority PAC, whose goal was to get Democrats elected to the US House of Representatives, spent a total of $30,752,440 in the 2012 election cycle. 46.46 percent of that money went towards elections where the group's preferred candidates emerged victorious.

Biggest Winners

Planned Parenthood Votes: 98.58% Return on Investment

Planned Parenthood Votes, the Super PAC associated with Planned Parenthood, spent a total of $5,086,007 in the 2012 election cycle. The group earned a whopping 98.58 percent return on investment.

Planned Parenthood Action Fund: 97.82% Return on Investment

Planned Parenthood Action Fund Inc., a "dark money" 501(c)(4) associated with Planned Parenthood, spent a total of $6,886,468 in the 2012 elections cycle. 97.82 percent of that money went towards elections that ended in the group's desired results.

Majority PAC: 87.86% Return on Investment

Majority PAC, the sister PAC to the Patriot Majority USA "dark money" group and whose goal was "protecting the Democratic Senate majority in 2012," spent a total of $37,477,541 in the 2012 election cycle, and achieved a 87.86 percent return on investment.

SEIU PEA-Federal: 84.65% Return on Investment

The Service Employees International Union (SEIU) PEA-Federal PAC spent a total of $15,202,306 in the 2012 election cycle, and 84.65 percent of that money backed winning candidates.

League of Conservation Voters: 78.17% Return on Investment

The League of Conservation Voters Inc. spent a total of $10,897,016 on the 2012 election cycle. 78.17 percent of that money backed winning candidates.

Worker's Voice: 76.14% Return on Investment

Worker's Voice, the Super PAC associated with the AFL-CIO, spent a total of $5,878,449 in the 2012 election cycle. 76.14 percent of that money was spent on elections that ended with the group's desired candidates winning.

SEIU COPE: 73.99% Return on Investment

The SEIU Committee on Political Education (COPE) spent a total of $14,594,501 in the 2012 election cycle. 73.99 percent of that money backed winning candidates.

Women Vote!: 73.16% Return on Investment

Women Vote!, a Super PAC associated with Emily's List, a well-known group supporting largely Democratic women candidates, spent a total of $7,887,648 in the 2012 election cycle. The group achieved a 73.16 percent return on investment.

The Congressional Leadership Fund: 60.64% Return on Investment

The Congressional Leadership Fund, a Super PAC focused on electing a House Republican majority, spent a total of $9,450,237 in the 2012 election cycle. 60.64 percent of those funds backed winning candidates.

American Action Network: 60.33% Return on Investment

American Action Network, a "dark money" 501(c)(4) whose purpose is to "create, encourage and promote center-right policies," spent a total of $11,785,919 on the 2012 election cycle, and achieved a 60.33 percent return on investment.

Americans for Tax Reform: 57.53% Return on Investment

Americans for Tax Reform [15], a "dark money" 501(c)(4) headed by anti-tax activist Grover Norquist [16], spent a total of $15,794,582 in the 2012 election cycle. 57.53 percent of that money went towards elections that ended in the group's desired results.