As relentlessly as the candidates have courted voters, they've also shown their love to donors.
A report by the Center for Responsive Politics places the total cost of the 2012 elections at an estimated $6 billion, which would make it the most expensive election in U.S. history
President Obama and Republican presidential nominee Mitt Romney both rejected federal public financing — another first — and each of them collected nearly as much as the entire field in 2004.
That's largely because many of the Watergate-era laws limiting campaign money have been nullified or circumvented. The 2012 presidential election cycle marks the first since Citizens United, the Supreme Court ruling that swept away key restrictions on money from corporations and the wealthy.
Each side had its strength.
President Obama's 4 million small donors have contributed online or even by text message.
Romney has been more successful in luring big-money backers, including those who have made contributions of a million dollars or more, to superPACs and so-called social welfare organizations. The names of donors giving to social welfare groups don't need to be disclosed.
Sheila Krumholz, executive director of the nonparitsan Center for Responsive Politics, says the big donors to outside groups — on both sides — have their own agendas.
"There is an expectation, I think, among many of these individuals that the rewards will go beyond mere gratitude," Krumholz says.
The clout of pro-Republican outside groups is even clearer in Senate and House races.
Political scientist Tony Corrado says that's because statewide and district-wide campaigns are relatively cheap.
"As you think about it, you know, one donor can finance the entire advertising for an independent group in a particular Senate or House race," Corrado says.
So then the question is: What happens when the candidates don't have the most prominent voices in the campaign?
It's already happening, according to an NPR analysis of data from ad-tracking firm Kantar Media CMAG. Pro-Republican groups in Virginia have run four times as many ads as their candidate, George Allen. In Ohio, they've spent twice as much on broadcast ads as Senate candidate Josh Mandel and the state GOP.
Corrado says the outside groups are pulling political power away from the traditional party organizations.
"Many of the groups that were active in 2010 were even more active in 2012, and I expect we'll see them active in 2014 and 2016."