The top three individual donors to super PACs this political cycle are all Democrats, according to an analysis of data downloaded from Sunlight's Real-time Federal Campaign Finance tracker. That's a huge turnaround from 2012, when the top three spots all went to GOP megadonors.

Whether that trend will hold isn't clear. With five months left before the election, torrents of cash will continue to flow into campaigns, and a few donors dropping $5 million apiece could upend this calculus. Moreover, the Republican groups that spend the most, such as Crossroads GPS and groups run by affiliates of Charles and David Koch don't report their donors at all. Sunlight's analysis of ad spending at one TV station in the competitive North Carolina senate race through mid-June found just 27 percent of Republican-sponsored ads were aired by groups that disclosed their donors. So it's clear that the biggest GOP groups aren't hard up for cash.

Because the final round of filings was due Sunday at midnight, this list is necessarily preliminary. We summed up contributions to super PACs and "hybrid" super PACs from January 1, 2013 through the end of June, leaving out donations from unions, corporations and other political groups as well as contributions "earmarked" towards a separate committee. We've subtracted refunds wherever we've found them, though political committees are notoriously bad about reporting this consistently. Note that these totals do not include candidates or party committees; the data refer to super PAC contributions only.

DonorStateParty LeaningAmount (million $)
Tom Steyer California D $20.2
M. Bloomberg    New York I $9.4
Fred Eychaner Illinois D $5.7
Paul Singer New York R $4.8
Richard Uihlein Illinois R $3.5
Bob Perry Texas R $3.1
Robert Mercer New York R $3.0
James Simons New York D $3.0
Jerry Perenchio California R $2.0
Virginia James NJ              R $1.8

The top donors

  1. Tom Steyer topped the list, donating just over $20 million. Steyer, a billionaire California hedge-fund manager, has been a major benefactor to groups working to combat climate change. He runs the NextGen super PAC which aims to elect pro-environment candidates. Steyer gave $5 million to the Senate Majority PAC, about $1.8 million to the CE Action Committee and $13.4 million to the NextGen Climate Action Committee.

  2. Michael Bloomberg, the former mayor of New York, donated about $9.4 million, including $6.4 million to Independence USA, the super PAC he runs. Since leaving office in New York, Bloomberg has stepped into the role of one of America's leading crusaders to strengthen gun laws and his PAC has lavished funds on supportive candidates. Bloomberg, a longtime registered political independent, also gave $2.5 million to the Senate Majority PAC, and lesser amounts to Americans for Responsible SolutionsMississippi Conservatives and West Main Street Values.

  3. Fred Eychaner, a Chicago based media baron, spent $5.6 supporting Democratic-leaning super PACs this cycle. In 2012, Eychaner gave about $14 million to Democratic super PACs. This cycle Eychaner gave $4 million to the Senate Majority PAC, $1.5 million to the House Majority PAC and $150,000 to Battleground Texas.

  4. Hedge-fund manager Paul Singer, the top Republican on the list, gave about $4.8 million. At $1.8 million, the biggest recipient was the American Unity PAC, which Singer launched to help Republicans who support gay marriage. Singer also gave $1.4 million to Ending Spending Action Fund, $1.25 to American Crossroads and lesser amounts to the Campaign for Jobs and Opportunity,John Bolton Super PACNew York 2014 and the USA Super PAC.

  5. Richard Uihlein, a Chicago-area businessman, has long been a supporter of Tea Party causes. This cycle, Uihlein gave $3.5 million to at least seven different right-leaning PACs; he also was refunded $200,000 from the Club for Growth. In past cycles, he has given nearly $4 million to Tea Party candidates and several million in his home state of Illinois.

  6. Though Bob Perry passed away in April, he still was the sixth largest donor this cycle, according to our analysis. Perry gave $3.1 million to GOP super PACs, including $2 million to Texans for a Conservative Majority and $1 million to Senate Conservatives Action. In the past, Perry helped bankroll the Swift Boat Veterans for Truth issue ads attacking then presidential-candidate John Kerry during the 2004 elections.

  7. James Simons, a New York-based hedge-fund manager, donated just over $3 million to left-aligned super PACs this cycle, include $2 million to the Senate Majority PAC and $1 million to the House Majority PAC.

  8. Robert Mercer is another New York-based hedge fund manager who has given several million dollars. This cycle, Mercer donated $3 million to conservative groups, including $1 million to the John Bolton super PAC and lesser amounts to New York 2014, Club For Growth ActionAmerican Heartland PACSenate Conservatives ActionUS Jobs Council and others.

  9. Jerry Perenchio gave $2 million to American CrossroadsPerenchio is the founder of the Univision television network and lives in a Los Angeles mansion that was used for the exterior shots for "The Beverly Hillbillies." In 2012, Sunlight counted at least $50 million Perenchio and his wife had given to political causes over the decades.

  10. Virginia James of New Jersey has been a major supporter of Club for Growth, a conservative super PAC, and is a strong advocate of school vouchers. She's given $1.5 million to Club for Growth this cycle, as well as contributions to Women Speak Out PAC and American Commitment Action Fund.

While fewer megadonors hogging the spotlight, this year has seen a number of lesser-known donors step up and open their wallets.

Ronald Firman, a Miami-based retiree, donated $1.46 million this cycle. Firman, along with a Las Vegas lawyer named Martin Burns, started the Values are Vital super PAC earlier this year. Firman initially donated even more, but refunded himself $672,679.

Seth Klarman, a Boston-based investor dubbed by the The Economist as "The Oracle of Boston," gave $1.7 million right-leaning PACs, including $1 million to Singer's American Unity PAC.

Warren Stephens, an investment banker, gave $1.4 million to right-leaning super PACs. Stephens, who's based in Little Rock, Arkansas, has been known to remix former Confederate anthems with contemporary subject matter, such as the plight of Wall Street, according to this Arkansas Times article. His contributions include $750,000 to American Crossroads, and $500,000 to the John Bolton super PAC.

Annie Earhart, the heiress to the J. Paul Getty oil fortune, gave $1.35 million to left-aligned super PACs. Earhart had given about $250,000 to an Obama-affiliated super PAC in 2012. The biggest recipient of her largesse this cycle has been American Bridge, the Democratic opposition research giant.

Sacramento-based developer Angelo Tsakapoulous has given about $4.5 million to political races in his home state of California. This cycle, Tsakapoulous gave $1.347 to Americans for Common Sense, a super PAC that has advertised against Republicans in New York's 1st Congressional District.

The Sunlight Foundation is a nonprofit, nonpartisan organization that uses the power of the Internet to catalyze greater government openness and transparency, and provides new tools and resources for media and citizens, alike. A list of Sunlight's funders can be found here.