Elections are getting more expensive–but don't think that more people are giving money to political groups. Instead, a smaller universe of donors is giving more money, thanks to a series of court ruling in 2010 that led to an explosion of outside groups, like super-PACs, which can accept donations in unlimited amounts to run ads independently of the candidates they support.

The net result, according to a new report from the Center for Responsive Politics titled, "The 2014 midterms may well mark the election cycle in which the small donor got left behind."

"An analysis of the number of individual donors also shows that—despite the overall cost of this election inching up—there are fewer people donating to political organizations," the report states. 

The rise of billionaire donors after 2010 court rulings, including a new batch of wealthy Democratic-leaning contributors who've engaged in this year's midterms, are rewriting the system anew in time for the 2016 presidential campaign, CRP found. That marks a change from 2008 and 2012, President Barack Obama rewrote the national campaign finance playbook by building an army of small donors for his campaign. In 2012, 28 percent of the money he raised came from donors who gave less than $200; small donors represented just 12 percent of Republican Mitt Romney's campaign cash, according to the Campaign Finance Institute. 

In its latest report, the Center also issued a downward revision to its cost estimate of the 2014 congressional elections, but the bottom line hasn't changed: The projected total would still be a record for a midterm election. 

CRP's new analysis projects that the 2014 midterms will cost at least $3.67 billion, but down from an original estimate of about $4 billion issued last week. The 2010 midterms cost $3.63 billion; the 2012 congressional elections, which coincided with a presidential election, cost about $3.6 billion. (CRP issued the new projection after analyzing new fundraising reports and omitting some double-counting of spending in its previous estimate).

While the overall costs of the 2010 and 2014 midterms are comparable, there are differences in how the money was raised and spent, the CRP report notes. Disclosed outside spending will rise to 13 percent of total election expenditures in the 2014 election from about 8.5 percent in 2010, when the Supreme Court's Citizens United ruling in January loosened restrictions on independent political spending. Pegging the exact cost of an election is impossible because some political spending isn't reported to the Federal Election Commission. 

Read CRP's revised findings here.