501(c)(3). 501(c)(4). 527. You might have heard some of these numbers in passing and not known to what they refer. They are provisions in the tax code that allow organizations to incorporate as not-for-profits and raise unlimited money from donors who can hide their identity, for a while. In the 2004 election, the most infamous 527 committee -- Swift Boat Veterans for Justice -- ran ads questioning John Kerry's military record. The ads may have decided the election. The Center for Public Integrity, in its year-long study called The Buying of the President 2008, questions the hidden role these "soft" political dollars play. Sen. John McCain (R., Ariz.), the leading Republican nominee for the presidency, worked across the aisle with Sen. Russ Feingold (D., Wis.) to pass legislation making it harder to use soft money to influence campaigns by limiting donations to political parties. It became law in 2002. It immediately landed McCain in hot water with some conservatives, who said it impinged on freedom of speech. The Supreme Court overturned portions of the law last summer, ruling that the free-speech rights of a not-for-profit group, Wisconsin Right to Life, had been unconstitutionally restrained. The law failed to take soft money out of the equation. Independent groups have proliferated and will probably play an important role in this presidential election. Take MoveOn.org, for example. The group's members support Sen. Barack Obama (D., Ill.) and recently asked members to vote on possible ads to air on his behalf. Obama also had help from the Services Employee International Union, an influential union that primarily represents health-care industry workers. Another group of aligned independents, Vote Hope and PowerPac.org, organized for him in California. Their activities included voter registration drives and political advertising in the state to the tune of at least $4 million.