Factbox: The wealthy behind U.S. presidential campaigns

(Reuters) - The campaigns of U.S. presidential candidates are limited to receiving donations of up to $2,500 per person, once for the state-by-state party nominating season and again for the general election. But independent "Super PACs" have no limits on what they can raise from individuals, corporations or labor unions.

Here is a look at wealthy individuals who have contributed at least $500,000 to the major political action committees (PACs).

RESTORE OUR FUTURE

Total raised as of January 31: $36.8 million

(Supports former Republican Massachusetts Governor Mitt Romney)

* Bob Perry - Houston builder who was a major donor to Swift Boat Veterans for Truth in 2004 and is a longtime supporter of Texas Governor Rick Perry. Donation: $1 million

* F8 LLC and Eli Publishing - Provo, Utah-based firms that share an address. Both have been linked to former executives of Nu Skin. Total donations: $2 million

* Paul and Sandra Edgerly - Paul Edgerly, of Brookline, Massachusetts, is an executive with Bain Capital, the private equity firm Romney co-founded. The Edgerlys each have given $500,000. Total donation: $1 million

* Robert Mercer - New York hedge-fund manager at Renaissance Technologies. Donation: $1 million

* Julian Robertson - hedge-fund industry legend at Tiger Management. Donation: $1 million

* Rooney Holdings Inc - A private investment firm formed in 1980s to acquire the Manhattan Construction Co. and since expanding into many areas. Donation: $1 million

* Paul Singer - hedge-fund manager who helped finance efforts to legalize gay marriage in New York. Donation: $1 million

* J.W. Marriott Jr. - chairman and CEO of Marriott International, brother of Richard Marriott. Donation: $750,000

* Richard Marriott - chairman of Host Marriott International. Donation: $750,000

* Oxbow Carbon - a Florida-based firm run by Bill Koch that sells coke, a key ingredient in aluminum manufacturing. Donation: $750,000

* Chris Shumway - a prominent Connecticut hedge-fund manager who got his start working with Robertson's Tiger Management. Donation: $750,000

* Miguel Fernandez - chairman of MBF Healthcare Partners, a private equity firm. MBF Family Investments also donated to the Super PAC. Donation of each: $500,000

* Steven Webster - a Houston-based investor and co-CEO of Avista Capital Partners, a private equity firm focused on energy, media and healthcare. Donation: $500,000

* David Lisonbee - founder of 4Life Research, a nutrition research firm in Sandy, Utah. Donation: $500,000

WINNING OUR FUTURE

Total raised as of January 31: $13.1 million

(Supports Republican former House of Representatives Speaker Newt Gingrich)

* Sheldon Adelson - billionaire Las Vegas casino magnate who built the Venetian hotel and casino. Donation: $5 million

* Miriam Adelson - doctor, wife of Sheldon Adelson. Donation: $5 million

* Harold Simmons - billionaire Dallas banker and pioneer of leverage buyouts, chairman and CEO of Contran Corp. Initially supported Rick Perry. Donation: $1 million

* Sivan Ochshorn and Yasmin Lukatz - step-daughters of Sheldon Adelson. Total donation: $750,000

* William Propst - real estate investor in Huntsville, Alabama. Donation: $500,000

AMERICAN CROSSROADS

Total raised as of January 31: $23.3 million

(Supports Republican candidates for federal offices)

* Harold Simmons - billionaire Dallas banker and CEO of Contran Corp. who has contributed to PACs supporting Rick Perry and Newt Gingrich. Donation: $10 million

* Contran Corp. - Dallas-based maker of titanium components. Donation: $2 million

* Whiteco Industries - Indiana-based company involved in advertising, construction entertainment and hotels. Donation: $1 million

* Crow Holdings - Dallas-based company with real estate and other interests. Donation: $500,000

* Philip Geier - New York-based executive. Donation:

$500,000

* Kenny Troutt - Dallas-based billionaire and founder of Excel Communications. Donation: $500,000

RED WHITE AND BLUE FUND

Total raised as of January 31: $2.8 million

(Supports former Pennsylvania Republican Senator Rick Santorum)

* Foster Friess - billionaire investor from Jackson, Wyoming, and founder of the PAC. Donation: $1 million

* William J. Dore - founder of Global Industries, president of Dore Energy Corp. Donation: $1 million

ENDORSE LIBERTY

Total raised as of January 31: $4 million

(Supports Texas Republican Congressman Ron Paul)

* Peter Thiel - billionaire co-founder of online U.S. payment service PayPal; first outside investor in Facebook. Donation: $2.6 million

PRIORITIES USA ACTION

Total raised as of January 31: $4.2 million

(Supports President Barack Obama)

* Service Employees International Union Committee on Political Education - union representing more than 2 million workers. Donation: $1 million

(Reporting by Alina Selyukh; Editing by David Lindsey and Philip Barbara)