Factbox: The wealthy behind presidential campaign

(Reuters) - The campaigns of U.S. presidential candidates are limited to receiving donations of up to $2,500 per person. 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 $250,000 to the major political action committees (PACs).

RESTORE OUR FUTURE

Total raised as of December 31: $30.2 million

(Supports Republican former Massachusetts governor Mitt Romney)

More than 27 donors contributed more than $250,000. Here are the top 10:

* 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 fund the efforts to legalize gay marriage in New York. Donation: $1 million

* 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

* Bob Perry - Houston builder who was a major donor to Swift Boat Veterans for Truth in 2004. A long-time Rick Perry supporter, he also gave $100,000 to the pro-Perry PAC. Donation:

$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

* W/F Investment Corp - a private debt and equity firm based in Los Angeles. Donation: $275,000

WINNING OUR FUTURE

Total raised as of December 31: $2.1 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 (not reflected in the PAC's fundraising filing on Tuesday because the donation was made in January, after the December 31 cutoff for the FEC reporting period)

* Miriam Adelson - doctor, wife of Sheldon Adelson. Donation: $5 million (also made in January )

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

* Harold Simmons - billionaire Dallas banker and pioneer of leverage buyouts, chairman and CEO of Contran Corp. Initially supported Texas Governor Rick Perry. Donation: $500,000

* Sivan Ochshorn - step-daughter of Sheldon Adelson. Donation: $500,000

* Yasmin Lukatz - casino executive in Las Vegas and step-daughter of Sheldon Adelson. Donation: $250,000

AMERICAN CROSSROADS

Total raised as of December 31: $18.2 million

(Supports Republican candidates for federal offices)

* Harold Simmons - billionaire Dallas banker and pioneer of leverage buyouts, chairman and CEO of Contran Corp. has contributed to PACs supporting Rick Perry and Newt Gingrich. Donation: $5 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. Donations:

$500,000

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

* Richard Gilliam - owner of Cumberland Resources, a Virginia-based coal company. Donation: $250,000

RED WHITE AND BLUE FUND

Total raised as of December 31: $729,935

(Supports former Pennsylvania senator Rick Santorum)

* Foster Friess - billionaire investor from Jackson, Wyoming and founder of the PAC. Donation: $331,000

* John Templeton Jr. - philanthropist and retired surgeon, son of stock investor John Templeton. Donation: $250,000

MAKE US GREAT AGAIN

Total raised as of December 31: $5.5 million

(Supported Texas Governor Rick Perry, who left the Republican race in January)

* Contran Corp. - Dallas-based maker of titanium components. Donation: $1 million

* S. Javaid Anwar - president, Midland Energy Inc. Donation:

$250,000

* Brint Ryan - CEO of Ryan LLC, a tax services firm. Donation: $250,000

* Tony Buzbee - lawyer in Houston. Donation: $250,000

* Darwin Deason - billionaire computer services entrepreneur. Donation: $250,000

* Kelcy L. Warren - CEO, Energy Transfer Partners in Dallas. Donation: $250,000

OUR DESTINY

Total raised as of December 31: $2.7 million

(Supported former Utah governor Jon Huntsman, who left the Republican race in January)

* Jon Huntsman Sr. - billionaire father of the candidate and executive chairman of the Huntsman Corp., a chemical company. Donation: $1.9 million.

* Robert D. Arnot - chairman, Research Affiliates LLC. Donation: $250,000

ENDORSE LIBERTY

Total raised as of December 31: $1 million

(Supports Texas congressman Ron Paul)

* Peter Thiel - billionaire co-founder of online U.S. payment service PayPal; first outside investor in Facebook. Donation: $900,000

PRIORITIES USA

Total raised as of December 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

(Editing by Will Dunham)