In Republican Race, a New Breed of Superdonor Last June, Harold C. Simmons, a wealthy Texas businessman, sent a $100,000 check to Americans for Rick Perry, a "super PAC" preparing for Mr. Perry's entry into the presidential race. A few months later, he donated $1 million to a different pro-Perry group through his company. In December, Mr. Simmons wrote another check, this one for $500,000, to Winning Our Future, a super PAC supporting Newt Gingrich. But Mr. Simmons was not done. In mid-January, as Mr. Gingrich was headed toward a victory in the South Carolina primary, Mr. Simmons wrote a $100,000 check to Restore Our Future, the super PAC supporting Mitt Romney. And toward the end of the month, as Restore Our Future used his money to help bludgeon Mr. Gingrich with attack ads in Florida, Mr. Simmons sent yet another $500,000 check to Mr. Gingrich's super PAC. "He generally supports conservative Republican candidates," said Chuck McDonald, a spokesman for Mr. Simmons. I assume he was just trying to be helpful. Mr. Simmons's contributions - all told, he has given more than $14 million to Republican super PACs so far this cycle - make him the exemplar of a new breed of superdonor in presidential politics. About two dozen individuals, couples or corporations have given $1 million or more to Republican super PACs this year, an exclusive club empowered by the Supreme Court's Citizens United decision and other rulings to pool their money into federal political committees and pour it directly into this year's presidential campaign. Collectively, their contributions have totaled more than $50 million this cycle, making them easily the most influential and powerful political donors in politics today. They have relatively few Democratic counterparts so far, with most of the leading liberal donors from past years giving relatively small amounts - or not at all - to the Democratic super PACs. And unlike in past years, when wealthy donors of both parties donated chiefly to groups that were active in the general election campaign, the top Republican donors are contributing money far earlier, in contests that will determine the party's presidential nominee. What unites them? They're economic conservatives," said Christopher J. LaCivita, a Republican strategist who helped advise Swift Boat Veterans for Truth, a forerunner of this cycle's super PACs, and who in 2008 co-founded another Republican advocacy group, the American Issues Project, that ran advertisements against President Obama. "Most of these guys are serious business tycoons," Mr. LaCivita added. They've built something big - usually something bigger than themselves. Some of the superdonors, like Mr. Simmons and Robert J. Perry, a Texas homebuilder, are longtime backers of independent groups that were active in past campaigns, like the Swift Boat group, which in 2004 challenged the Vietnam War record of Senator John Kerry, the Democratic presidential nominee. Several attend the exclusive, secretive gatherings of wealthy conservative donors hosted twice a year by the billionaire Koch brothers. Many move in the same social or political circles: Sheldon Adelson, a billionaire casino executive who is close to Mr. Gingrich, serves on the board of the Republican Jewish Coalition with Paul Singer, a hedge fund executive and a top contributor to Restore Our Future. Some of the million-dollar-plus donors, however, are relatively new to the world of big-league political giving and appear to be motivated by personal connections to particular candidates. Paul B. Edgerley and his wife, Sandra, for example, together gave $1 million to the pro-Romney super PAC. Mr. Edgerley is an executive at Bain Capital, Mr. Romney's former firm. A few of the megadonors gave through limited liability companies, shielding their identity. One $1 million donation to Restore Our Future came from F8 LLC, a company whose listed address in Utah leads to an accounting firm. A charitable foundation linked to Sandra N. Tillotson, co-founder of the skin care company Nu Skin, uses the same address. Ms. Tillotson was reimbursed by Restore Our Future in July for what appeared to be costs associated with a fund-raiser at her New York apartment. Jim Rutenberg contributed reporting.