Longest Campaign On Road To Costliest

In Iowa, independent political groups have upped the ante on the longest and (probably) most expensive president campaign in history, spending $5 million in the two week period that ends with Thursday night's caucuses.

For example, Service Employees International Union has spent $1,560,000 for ads supporting John Edwards in the Democratic race, and AFSCME has spent $770,000 to support Hillary Clinton. The Club for Growth has spent $700,000 criticizing Republican Mike Huckabee.

But candidates are spending madly as well. Mitt Romney simply taps his bank book -- he has spent $45 million nationwide; it's not known how much went to Iowa, where he has reportedly outspent his opponents. Barack Obama reportedly has spent the most on Iowa TV ads of any candidate: $9 million. TV spending in Iowa is triple 2004 levels.

There are four types of advocacy groups that fund political campaigns. Political parties are the oldest. Their role in campaign finance was curtailed by a 2002 law and US Supreme Court ruling.

Political Action Committees (PACs) are the next best-known group and began in 1944. They raise "hard" money for the express purpose of defeating or electing candidates. There are limits on how much money an individual can contribute to a PAC and on how much a PAC can contribute to a candidate or a party. Most of us associate PACs with business, labor or ideology. However, politicians often form what is called a Leadership PAC to raise money to help fund other candidate campaigns. Politicians do this because they have their eye on a leadership position in Congress or a higher office; it's a way of currying favor.

The other two types of political advocacy groups solicit "soft money" which is used for voter mobilization and "issue ads" that do not expressly call for the election or defeat of a candidate. There is no limit on individual soft money contributions.

Read more: Does Iowa matter? Also, see Third Quarter Presidential Fundrasing, The Campaign for President: Is It Worth the Cost? and Money, Politics and Advocacy. From Deborah White: Late Iowa Buzz: Edwards Up, Obama & Clinton Steady and Grim