Sheldon and Miriam Adelson attend the opening ceremony of Four Seasons Hotel in Cotai Strip in Macau, Aug. 28, 2008. Kin Cheung/AP hide caption

itoggle caption Kin Cheung/AP

Amy Goldman, known for her gardens and her illustrated coffee-table books about plants, has donated $1 million to a pro-Obama superPAC. Sandi Fellman hide caption

itoggle caption Sandi Fellman

Bill Koch (center) celebrates his team's 1992 America's Cup win. Koch, the brother of billionaire GOP donors Charles and David, has given $2 million to the superPAC backing Mitt Romney. Vince Bucci/AFP/Getty Images hide caption

itoggle caption Vince Bucci/AFP/Getty Images

PayPal co-founder Peter Thiel, who has donated more than $2.5 million to a superPAC backing GOP presidential candidate Ron Paul, speaks at the National Press Club in Washington, D.C., in October. Chip Somodevilla/Getty Images hide caption

itoggle caption Chip Somodevilla/Getty Images

Dreamworks Animation CEO Jeffrey Katzenberg, shown at CinemaCon 2012, has donated $2 million to the pro-Obama superPAC Priorities USA Action. Chris Pizzello/AP hide caption

itoggle caption Chris Pizzello/AP

Hedge fund manager Paul Singer of Elliott Management has donated $1 million to Mitt Romney's superPAC. Lucas Jackson/Reuters/Landov hide caption

itoggle caption Lucas Jackson/Reuters/Landov

In a video from the Horatio Alger Association, William Doré tells of a tense and abusive childhood. Horatio Alger Association/YouTube hide caption

itoggle caption Horatio Alger Association/YouTube

J.W. Marriott dines with his son Bill in a Hot Shoppe in March 1969. The elder Marriott was close to Mitt Romney's father, George. Dennis Brack /Landov hide caption

itoggle caption Dennis Brack /Landov

Foster Friess introduces Rick Santorum at the 2012 CPAC Conference in Washington, D.C., on Feb. 10 wearing a sweater vest embroidered with the candidate's name. Ron Sachs/CNP DPA/Landov hide caption

itoggle caption Ron Sachs/CNP DPA/Landov

Bill Maher, shown here at a 2011 event in Los Angeles, gave $1 million to the superPAC supporting President Obama's re-election bid. Chris Pizzello/AP hide caption

itoggle caption Chris Pizzello/AP

Texas businessman Harold Simmons stands outside a Dallas courthouse in this 1997 photo. Flor Cordero/Reuters /Landov hide caption

itoggle caption Flor Cordero/Reuters /Landov

Sheldon Adelson speaks at the 2008 "Facing Tomorrow" Presidential Conference in Jerusalem. David Silverman/Getty Images hide caption

itoggle caption David Silverman/Getty Images