Presidential candidates spent $1.8 billion running for office in the 2008 election cycle. In the 2010 mid-terms, $3.9 billion was spent on Congressional elections. The 2012 elections are expected to break new records in campaign finance. Here's a look at where that money comes from and how it's used.
Note: PACs, or political action committees, are special interest groups formed around issues, candidates or both. The July 2010 Supreme Court ruling in SpeechNow.org v. Federal Election Commission established the legal precedent for groups informally referred to as Super PACs, or independent expenditure committees. These groups may raise unlimited amounts of money from corporations, unions, associations and individuals, and then spend without limit to openly support or oppose candidates, but they are not allowed to contribute directly to campaigns.