WASHINGTON (AP) -- A U.S. presidential candidate's actual campaign is only one element in the contest for the White House.
Here's a look at all of the campaign-style organizations that presidential hopefuls and their allies can tap to chase the top prize in American politics.
When voters think of a presidential campaign, this is what comes to mind: a central organization with the candidate at its top. The candidate makes the strategic decisions in consultation with advisers, and the person whose name is on the ballot has the final say.
A campaign is limited in how much cash it can raise from donors -- a maximum of $2,700 for the primary and another $2,700 for the general election. The names of those donors, and how the money is spent, must be disclosed to the Federal Election Commission.
To be sure, these traditional campaigns exist. But there's so much more.
POLITICAL ACTION COMMITTEES
A group that raises and spends money to influence the outcome of elections. A PAC is limited in how much it can give and raise from individuals, other PACs or party committees in a calendar year. Many are sponsored by trade associations or members of labor unions. PACs must disclose to the FEC where they get their money and how they spend it.
These have been around for years. But there's a new twist on this front.
A pair of Supreme Court decisions in 2010 gave rise to a new kind of political action committee, known as super PACs. These groups can raise unlimited amounts of money from donors, including corporations and groups such as labor unions. They can spend unlimited amounts of money to advocate for and against candidates for office, but cannot directly fund a candidates' political machine.
Super PACs are not allowed to coordinate their actions with candidates or campaigns. In short, they can't talk with the people they're spending money to support. Super PACs must disclose their donors and how they spend their cash to the FEC.
They've become huge players in the campaign landscape.
Taking their name from part of U.S tax code, a 527 can raise unlimited amounts from individual donors, labor unions and corporations. They cannot, however, expressly tell voters how to cast ballots, nor can they give money to candidates. They must disclose their finances, but do so much slower to the IRS than PACs and super PACs report to the FEC.
The Republican Governors Association, for instance, is an example of a group that is incorporated in this structure.
501(c)3 and 501(c)4
These are tax-exempt non-profits known as social welfare groups. In the eyes of the U.S. federal tax agency, they are charities -- the Humane Society of the United States, for example, is a 501(c)3.
A 501(c)3 can tell voters about candidates' positions, but cannot explicitly tell them how to cast a ballot. They can raise and spend unlimited amounts of money, and they disclose their donors to the Internal Revenue Service. The tax agency, however, does not make that information public.
The other type of tax-exempt social welfare group is a 501(c)4, which cannot have the primary goal of influencing elections. Rather, they exist to educate voters about issues and can do some limited political activity. They can raise and spend unlimited amounts, but voters cannot find out who is picking up the tab.
Much of the political machine backed by conservative billionaires Charles and David Koch operates in this way.