Eighteen incoming members of Congress each got more than $1 million in dark money donations during their recent campaigns, but many more have reason to resent the stealthiest of campaign contributions, a Sunlight Foundation analysis has found.

Dark money represents campaign contributions whose sources never have to be publicly reported. That's because the money is funneled through non-profit entities organized under a section of the tax code that protects them from having to name their donors. These kind of groups — such as the pro-GOP Crossroads GPS and the pro-Democrat League of Conservation Voters — have increased their electoral role in the wake of a series of court rulings that opened the door for unlimited corporate and union spending on campaigns. Nonprofit groups made more than $300 million of such donations during the course of the 2012 election cycle, the vast majority of that, $256 million, was spent during the fall campaign to influence general election races. 

While a number of members of the 113th Congress will have dark money to thank for helping them win their seats, even more won despite being targeted by an influx of cash from unnamed donors.

About one quarter of outside money spent on the general election was dark, according to a Sunlight Foundation analysis based on reports filed with the Federal Election Commission. That number is certainly an underestimate because tens of millions of dollars in election expenditures do not have to be reported to the FEC.

In more than two dozen House races, dark money accounted for $1 million of the campaign spending, but it was not always decisive. Of the 25 House candidates who were targets of the most dark money spending, only nine lost their races. 

The Haunted House

Though the vast majority of $256 million in dark money was spent on the presidential and Senate contests, it may have the most impact on the incoming members of the House that were helped by it. With less personal campaign resources than Senate or presidential office-seekers, the new House members owe an even bigger debt to these contributors.

There are nine incoming members of the House–two of whom were elected for the first time–who benefited from over $1 million in dark money in their general election races. The three candidates who were most helped by dark money are all Republicans: Rep.-elect Keith Rothfus of Pennsylvania, and returning freshmen Reps. Bill Johnson of Ohio, and Jeff Denham of California, considered one of his party's rising stars. Their races were inundated with more dark money than any others — and they will all be going to Washington in January.

Another big winner: Illinois Rep-elect Rodney Davis. The former executive director of his state's Republican party, Davis beat Democrat David Gill, an emergency room physician. Of the more than $2 million in dark money spent in the race, 99.8 percent of it was on Davis' side. 

Here is a list of the biggest dark money winners:

The dark money that helped these nine candidates represents 33 percent of the entire bounty of outside spending in their races. The winner who was most reliant on dark money, as a percentage: Rep. Scott Tipton, R-Colo. The freshman benefited from $1.6 million in dark money to outpace state Rep. Sal Pace; that amount represents two-thirds of the outside spending in the race. 

In the 25 House races hit with most dark money, 86 percent of such spending was designed to help Republican candidates, largely by paying for attack ads against their Democratic opponents. Only three of the 25 races featured more dark money spending against the Republican candidates. (And of those three GOP targets, two won anyhow: Reps. Dan Benishek, R-Mich. and Steve King, R-Iowa).  

Sunless Senate

Nine incoming senators got at least $1 million in dark money contributions to help them in the general election. The biggest beneficiary is one of the few GOP senators to win a close race–Rep. Dean Heller, R-Nev. More than $8 million in dark money ads targeted his Democratic opponent, Rep. Shelley Berkley. Senator-elect Tim Kaine of Virginia, who was part of the most expensive Senate race in the country in terms of overall outside spending, benefited from nearly $3 million in dark money–most of it for attack ads and mailers by the League of Conservation Voters, a 501(c)4 environmental group, targeting Kaine's Republican rival, former Sen. George Allen.

The group of dark money beneficiaries includes Elizabeth Warren, who was part of a pact with Sen. Scott Brown, whom she beat, to refuse any outside group spending on advertising; the dark money went towards robo-calls and direct mail instead. 

Even so, Kaine, Warren and most of the other senators saw more dark money spent against them than on their behalf. The only two winners that had more of the mysterious money on their side are Republicans: Heller and Jeff Flake of Arizona. 

Kaine, for instance, was hit with over $16 million in dark money–mostly from Crossroads GPS. He was the biggest target of dark money in the general election, followed by Sherrod Brown, D-Ohio, Berkley, Tammy Baldwin, D-Wis., Jon Tester, D-Mont., and Bill Nelson, D-Fla. Besides Berkley, all of those candidates won.

Brown has made an issue of campaign finance disclosure. He has called on the IRS to investigate whether nonprofits are abusing their tax-exempt status to run political campaigns. And, in his victory speech, he talked about the importance of the DISCLOSE Act, which would require any group that makes a campaign expenditure of $10,000 or more to disclose their top donors. The bill failed to pass the Senate in both 2010 and 2012.

Earlier this week, at a National Press Club conference recapping the influence of outside money at the 2012 election, former FEC Chairman Trevor Potter, who gained reknown this year as the lawyer for satirist Stephen Colbert's campaign committees, argued for end-arounding Congress to achieve campaign finance reform. Potter said Obama could replace the federal election commissioners, whom he argues have failed to enforce disclosure laws, with his own appointees. Doing so would require a departure from tradition, in which the White House, Senate and House leadership each got to choose two of the six commissioners.

Negative Darkness

To the surprise of no one who turned on their TV sets in the weeks leading up to Nov. 6, most of the dark money spending was negative. It was also pro-Republican money. In the Senate, 85 percent of it was in the form of independent expenditures criticizing a candidate and the vast majority of it went against Democrats. There was a similar story in the House, where 84 percent of the spending by groups that do not report donors was negative.

In the presidential race, pro-GOP dark money won out by a margin of 7 to 1. The majority of that bounty came in the form of negative ads against President Obama — at $55 million, but pro-Mitt Romney ads also totaled $29 million. Positive Obama ads and negative Romney ads came to about $12 million.

(Jake Harper contributed reporting.)