(CBS News) Super PACs, the political action committees permitted to accept and spend unlimited sums of money, are revealing an ever-widening roster of mega-donors. Through August, more than 60 donors gave at least $1 million to super PACs, which are required to disclose their donors' names and amounts.
At least 26 people or companies gave $1 million or more to the main super PAC supporting Mitt Romney, Restore Our Future, which had raised a cumulative $97 million by the end of August and spent $90 million. Its donor list included 25 billionaires.
At least 16 people or labor unions gave at least $1 million or more to the main super PAC supporting President Obama, Priorities USA Action, which had raised $43 million through August and spent $35 million. At least three billionaires gave to the pro-Obama group.
Super PACs supporting various candidates and causes have already spent a combined $270 million during Campaign 2012, according to the Center For Responsive Politics and the Sunlight Foundation, two non-profit research organizations tracking the money flow.
The Super PAC with the most money in the bank entering September was American Crossroads, the Republican-backing group co-founded by Karl Rove and Ed Gillespie. It had $32 million cash on hand, or quadruple the funds of the next most cash-rich group, House Majority PAC, which supports Democrats running for the U.S. House of Representatives.
Each of the nation's three leading super PAC donors - Sheldon Adelson, Harold Simmons, and Bob Perry - are conservatives who have contributed double-digit millions to a number of groups. They are soon to be joined by Joe Ricketts, who has stated he would spend $10 million of his fortune on political advertising this campaign season. A spokeswoman confirmed today that Ricketts did give another $10 million this month to Ending Spending Fund, a super PAC he founded.
As eye-popping as some of these donation totals may be, they do not include additional contributions by many of these donors to candidates' campaigns, to political parties, or to non-profits not required to disclose their donors. The latter category includes three conservative groups -- Americans For Prosperity, which has already spent $30 million on election activities, and the U.S. Chamber of Commerce and Club For Growth Action, which have each spent $13 million.
Here are the top 20 super PAC donors based on a CBS News review of their reports to the Federal Election Commission:
1. Sheldon Adelson & Family. Total: $37.5 million
Adelson is CEO of the Las Vegas Sands Corp.
Billionaire Adelson and his wife, Miriam, gave pro-Romney Restore Our Future $10 million in June. During the primary campaign, the Adelsons and their children bet heavily on Newt Gingrich, giving pro-Gingrich Winning Our Future $21.5 million; $5 million was refunded in May. The Adelsons are gave $5 million to the Congressional Leadership Fund, which supports Republican candidates for the House of Representatives, $5 million to the YG Action Fund, which supports conservative "young guns" running for office, and $1 million to Freedom PAC, which supports Florida Congressman Connie Mack's run for the U.S. Senate.
2. Harold Simmons/Contran. Total: $18.7 million
Simmons is CEO of Dallas-based holding company Contran Corp. and publicly-traded Valhi.
Billionaire Simmons and his company, Contran, gave $13 million to pro-Republican American Crossroads, $1.1 million to pro-Gingrich Winning Our Future, $1.1 million to two groups supporting Texas Governor Rick Perry, and $800,000 to the pro-Romney Restore Our Future. His wife, Annette, gave $1.2 million to pro-Rick Santorum Red White and Blue Fund. Simmons also gave $1.5 million to a pair of groups which promoted the U.S. Senate candidacy of Texas Republican David Dewhurst, who lost the primary to Ted Cruz - Conservative Renewal and the Texas Conservatives Fund - and $25,000 to Strong Utah, which supports Republican Senator Orrin Hatch.
3. Bob Perry. Total: $15.9 million
Perry is a Houston-based homebuilder and president of Perry Homes.
Perry gave $8 million to pro-Romney Restore Our Future and $6.5 million to American Crossroads. He also gave $1 million to the Congressional Leadership Fund, focused on electing Republicans to Congress, $300,000 to the Texas Conservatives Fund, which promoted the U.S. Senate candidacy of Texas Republican David Dewhurst, who lost the primary to Ted Cruz, and $100,000 to Make Us Great Again, a super PAC supporting Texas Governor Rick Perry.
4. Peter Thiel. Total: $4.7 million
Thiel is CEO of Clarium Capital Management, in Palo Alto, Calif.
Billionaire Thiel gave $2.6 million to pro-Ron Paul Endorse Liberty and $135,000 to pro-Paul Revolution PAC. He also gave $2 million to Club For Growth Action, which advocates for lower taxes.
5. Robert Rowling. Total: $4.13 million
Rowling is president of TRT Holdings, a Texas firm which owns Omni Hotels and Gold's Gyms.
Billionaire Rowling and his company gave $4 million to pro-Republican American Crossroads, $100,000 to pro-Romney Restore Our Future, and $35,000 to Texas Conservatives Fund, which promoted the U.S. Senate candidacy of Texas Republican David Dewhurst, who lost the primary to Ted Cruz.