2018, 2016 and 2014 total cost projections include spending by PACs on overhead expenses, which were all attributed to Congressional activity.

METHODOLOGY

Breaking with tradition, the Center for Responsive politics has modified how it calculates the total cost of federal elections. That's because the data provided by the FEC is now more detailed, allowing us to more carefully calculate the amount spent on election activities by PACs and candidates. The modified calculations affect only races from 2010 on; the more detailed data is not available for prior years, so we cannot update our estimates for earlier cycles. However, we do not expect figures for those years would be radically different, even had we access to more complete data, from those we show on our website.

The main components of our cost of election estimate are:

The amount of money congressional and presidential candidates reported having spent on their campaigns between Jan. 1, 2011 and Dec. 31, 2012. To prevent double counting, we excluded money donated from one candidate to another as well as money transferred to party committees. The amount of money party committees, including the DNC and RNC, spent on election activities in the same period. For these calculations, we excluded any money the party committees transferred to federal candidates or other party committees, as that money is eventually spent by those candidates and committees and is included elsewhere in this total. The total amount of money spent by 527 groups on federal elections. The total amount of "outside" spending we have been able to identify, including money spent on issue ads, electioneering communications, and independent expenditures. However, this includes only spending that was reported to the Federal Election Commission; spending on many issue ads is not reported. The amount spent by political action committees on "overhead" expenses, like salaries and office rentals. Much PAC money is spent on candidate contributions, but we include that money elsewhere. Spending by "host committees" and party committees on federal conventions.

To calculate spending on the presidential race, we only include money spent by presidential candidates, as well as money spent by outside groups that is designated as targeting a presidential candidate. We also include the cost of conventions and activity by the DNC and RNC in this total.