When it comes to campaign fundraising, Ohio U.S. Senator Sherrod Brown, a Democrat, has recently pulled ahead of his Republican challenger, State Treasurer Josh Mandel. However, Brown has been the target of more outside spending than any other member of Congress [3] and Mandel has enough support from outside "dark money" groups to close the gap.

Brown edges out Mandel in direct campaign fundraising, $15 million to $10 million [4], and is supported by the Democratic-aligned MajorityPAC, as well as a handful of national unions, Mandel has the support of powerful dark money groups, as well as the mysterious "Government Integrity Fund," a nonprofit evidently formed entirely to attack Brown. Here is a rundown of the big money in Ohio's U.S. Senate race and the TV ads those funds are bankrolling.

Majority PAC Attacks Mandel for Alleged Cronyism, Dereliction of Duty

Majority PAC, which is a SuperPAC operated [5] by the leadership of the Democrat-aligned dark money group Patriot Majority [6], has spent $2.3 million [7] in Ohio on attack ads against Mandel, starting in May, when the group ran an ad [8] accusing Mandel of not tending to his official duties as Ohio state treasurer in order to campaign for Senate. The group followed up with a similar ad [9] in June, which quantified the issue, claiming he missed "14 meetings of the board that invests our tax dollars." The Columbus Post-Dispatch, which investigated claims of Mandel's absence, reports that Mandel sent his chief financial officer to the meetings instead, and that "his predecessors as treasurer similarly skipped most of the Board of Deposit meetings," though the newspaper did point out that Mandel's predecessor "occasionally attended in person. Mandel has never done that."

Majority PAC's latest ad [10] instead attacks Mandel for staffing his office "full of college buddies and political cronies" while failing to "fight for Ohio jobs," the ad focuses on Mandel's failure to support the 2008 bailout of Ohio's auto industry, which saved 850,000 Ohio jobs. The ad relies on a study [11] by the Michigan-Based Center for Automotive Research.

Majority PAC has spent almost $17 million this election cycle [12]. Super PACs can accept unlimited contributions and spend unlimited amounts, but unlike the "dark money" nonprofits supporting Mandel, they must disclose their donors. Top donors [13] to Majority PAC include a variety of unions, as well as hedge fund manager Jamie Simons, who has given $1.5 million, and Chicago media mogul Fred Eychaner, who has contributed $800,000. Simons and Eychaner are also big donors to Priorities USA, the Super PAC formed exclusively to support President Obama's reelection.

Crossroads GPS Blames Brown for Jobs Numbers, "Government Takeover of Healthcare," Entire National Debt

On the other side, Crossroads GPS [14] has overcome Majority PAC's spending, dropping at least $3.5 million [7] in recent weeks on ads directly attacking Brown, plus millions more on ads that indirectly criticize the Democratic incumbent.

Crossroads GPS' latest "issue ad" [15] accuses Brown of siding with President Obama 95 percent of the time, which they allege will cost taxpayers "$500 billion in new taxes," likely a reference to the amount the Affordable Care Act raises [16] from individuals who do not purchase insurance or employers who refuse to supply it to their employees. So-called "issue ads" like these are not reported to the Federal Elections Commission unless they are run within 30 days of a primary or party convention, or 60 days of a general election, so amounts spent on earlier issue ads are not known.

Crossroads GPS [14] has made other expenditures in Ohio attacking both Obama and Brown in the same ad (one from July tells viewers [17] to "call Sherrod Brown," and "tell him we've got to take away Obama's blank check"), but it is not clear [18] whether these are reported as spending against Obama or Brown.

As a 501(c)(4) nonprofit organization, Crossroads GPS does not disclose its donors.

Backed by Big Oil, U.S. Chamber of Commerce Attacks Brown on Energy

Brown has also been targeted by the U.S. Chamber of Commerce [19], which, like Crossroads GPS [14], is not required to disclose its donors. The group has disclosed at least $2 million [7] in spending against Brown, but there is likely more, as Brown was the target of larger national campaigns in late 2011 and early 2012, outside the period of mandatory reporting for "issue ads." The Chamber characterized [20] its earlier spending as the largest "education and grassroots mobilization campaign" in its history.

The Chamber's Ohio ads have a tendency to focus on energy policy. Their most recent ad [21] claims that Brown voted for "costly regulations" and "against American energy security." Another from late 2011 makes similar claims [22], stating that Brown voted "to block American energy production," while another [23] from the same time claims that Brown "supports raising energy taxes."

When questioned about the ads, a Chamber spokesperson pointed to Brown's opposition to big oil subsidies and the expansion of offshore drilling [24], neither of which would have a substantial impact [25] on the price of gasoline in the next few decades.

The Chamber is a 501(c)(6) association, commonly referred to as a "business league." Its exact funders are unknown, though the Chamber claims that it gains support from dues collected from its member businesses, which include all major oil companies. One of the few known donations [26] to the Chamber is a 2010 payment from oil giant Chevron, totaling $500,000.

Other Chamber ads also attack Brown for supporting the Affordable Care Act, calling him "the architect of controversial public option" and "the deciding vote for Obamacare." A June investigation by the National Journal [27] revealed that the Chamber has received more than $100 million from insurance companies to fight against the Affordable Care Act.

Freedomworks for America Spends Big to Support Mandel

Amidst the mudslinging, Super PAC for the tea party-affiliated Freedomworks for America [28] has largely spent its $1.4 million [29] bolstering Mandel's image as a fiscally conservative "patriot."

Freedomworks [30] began running ads supporting Mandel and attacking Brown in mid-September, part of a larger, national ad buy [31] that targeted key congressional races in Arizona, Florida, Indiana, Ohio, and Virginia. Their ads feature Mandel giving an inspiring speech, while showing stills of Mandel serving in the U.S. Marines, and greeting voters around Ohio.

In addition to ads, Freedomworks has produced yard signs [32] and door hangers [33] in support of Mandel, as well as voter guides [34] attacking Brown for being "the most liberal member of Congress." (The same guide also calls Mandel "a true friend of individual liberty and the United States Constitution.") The Super PAC has also supported Mandel with phone banking operations and get out the vote efforts [35].

The Freedomworks for America Super PAC is required by law to disclose its donors. But in this case, that disclosure means very little. The Super PAC's top donor by far [36] is the Freedomworks 501(c)(4) nonprofit, which does not disclose its donors.

"Government Integrity Fund" Praises Mandel, Attacks Brown, Claims it Isn't Playing Politics

Mandel is also receiving support from "The Government Integrity Fund," a previously unknown group that began moving money into the Ohio race back in May. The group, another 501(c)(4) which is not required to disclose its donors, has spent over $1 million [37] supporting Mandel and attacking Brown, and has no other disclosed purpose or known activities. In past ads [38], the Fund has praised Mandel's service in Iraq, and claimed that he is "fighting for taxpayers" in Ohio. The Fund has also run an ad [39] attacking Brown for taking money from Wall Street and voting to "kill the balanced budget amendment."

The Fund is running these ads despite claiming on their incorporation papers [40], filed with the IRS, that they will not spend "any money attempting to influence the selection, nomination, election, or appointment of any person to any Federal, state, or local public office." The Fund's website [41] provides no information on the group's leadership or agenda, and its mailing address is listed as a PO box in Columbus, Ohio. The only known employees [42] of the Fund are Tom Norris, an Ohio lobbyist, and Joel Riter, who also works at Norris' lobbying firm and until recently had a top role on the Mandel campaign. The source of the Fund's money remains unknown.

National Education Association Says Mandel is a "Pawn of Big Insurance"

Mandel has encountered strong resistance from the National Education Association (NEA), one the nation's largest unions, which has directed $1 million [43], more than half the money they have spent this election cycle, to the race. The money comes from the organization's national PAC, which discloses all its donors and relies on voluntary contributions from teachers across the country.

NEA's ads characterize Mandel as a pawn of large insurance companies, their most recent ad [44] features a special education teacher who criticizes Mandel for wanting to "allow insurance companies to deny coverage for pre-existing conditions," and says that Mandel voted to allow insurance companies to "deny coverage for autism." The ad references Mandel's "no" vote on Ohio HB. 8 [45], which prohibits health insurance companies from denying coverage for services necessary for individuals diagnosed with autism spectrum disorders. The NEA has also run ads attacking Mandel's likely support for GOP plans to overhaul Medicare [46], which the ad says will vastly increase the cost of care in order to fund tax cuts to "millionaires and billionaires."

The latest polls [47] show a close race, with Brown edging out Mandel by five points, according to the average of Real Clear Politics polling data. With less than a month to go, outside money from either side may decide the race.