While super PACs, seven-figure checks and the heated Republican presidential nomination fight that Mitt Romney eventually won dominated the news the first half of this election year, congressional campaigns quietly have been pumping hundreds of millions of dollars into the political economy — and the real avalanche of congressional campaign expenditures and campaign ads is yet to begin.

Outside spending groups like the Campaign for Primary Accountability and Freedomworks for America have gotten most of the spotlight for running ads attacking incumbents in primaries. But congressional candidates themselves have had far more to spend to get their message out. As of mid-May, congressional campaigns had spent a total of $557 million. Of that, some $69 million, one-twelfth of their total expenditures, went for advertising.

A preliminary analysis of Federal Election Commission reports suggests that ad spending is running behind what it was at this point in the last two election cycles. Those figures could change quickly, because the stretched-out primary schedules for congressional campaigns mean that not all have reported their pre-primary spending. But some experts theorize that the relatively slow start to congressional campaign spending is a reflection of a changed landscape where outside groups have become a bigger factor.

“2012 is a very difficult election for both parties and all independent groups and that will add to the unpredictability and overall wariness of all players, especially if they feel that they cannot control the real deciding factors in the election,” said campaign strategist and president of Patriot Majority PAC, Craig Varoga.

* Ad expenditures with obviously incorrect dates were not included for this graph.

What the above chart does not show is the spending by outside groups, supplementing what campaigns are spending. These groups, including super PACs, nonprofits, labor unions, individuals and corporations have reported spending a total of $45.5 million so far to influence congressional races. Like the groups that spent money in the presidential race, these organizations have also made an impact in some competitive races, challenging entrenched incumbents or tilting the playing field for politicians vying for a nomination.

Comparing super PAC and campaign ad spending

In some high-profile races, non-profit groups — and even individuals — appear to be acting as media arms for their chosen candidates.

• Last month, when Tea Party candidate and Indiana state treasurer Richard Mourdock defeated Sen. Dick Lugar, R-Ind., the third longest-serving member of the Senate, right-leaning super PACs spent more than $3.92 million to oppose Lugar and support Mourdock. Lugar had a $1.16 million ad and media campaign, compared to Mourdock's $532,000 advertising effort. But Club for Growth, the anti-tax, anti-regulatory group, topped the veteran senator's expenditures, spending $1.65 million on media. Club for Growth's expenditures came through three entities: Club for Growth Action, a super PAC, Club for Growth PAC, a political action committee and Club for Growth, a nonprofit organized under section 501(c)4 of the tax code.
• Thomas Massie, who recently won the Republican nomination in Kentucky’s 4th district, spent a meager $76,000 on ads, while Liberty for All, a super PAC headed by a few twenty-somethings drawn to politics by Ron Paul’s libertarian ideas, backed him by spending more than $500,000.
• In big money races, super PACs can make a difference for underfunded candidates, even those who raise millions. Take Texas' Senate race. David Dewhurst, the current lieutenant governor of the state, is facing a runoff against Ted Cruz, a former state solicitor general. They've both spent millions on the campaign, and super PACs have spent more than $6.7 million, as they battle for the seat that will be vacated this year by retiring Sen. Kay Bailey Hutchison, R-Texas. Dewhurst has raised more than $13 million — $6 million of it his own money. 

Cruz, who's raised $5.8 million, has spent $2.06 million on ad buys. But he has benefited from heavy Club for Growth support, which has spent more than $2.4 million attacking Dewhurst. Dewhurst has had the money to hit back, however: He has spent a total of $6.75 million on ad buys, the most among candidates running for office. Among the ads he has run is a controversial piece that calls Cruz a proponent of Chinese interests.

Aides to candidates insist they see the outside groups as a wild card rather than as an auxiliary. Massie’s campaign said that the super PAC's big ad buys made them nervous. “When we heard about Liberty for All and about their spending we had reservations till they posted their first ad, till then there was a little bit of anxiety.” Phil Moffett, Massie’s campaign spokesperson said. “You have no idea what they are going to do,” he said.

Democrat Varoga, himself running a super PAC, agrees that “Independent and outside players can cut both ways,” Varoga said. “It can keep a campaign alive, for at least a while, as happened when Sheldon Adelson spent millions earlier this year–pumping millions into the Republican primaries to prop up Newt Gingrich. Or they can throw a campaign off message, as Donald Trump did to the Romney campaign by reintroducing the birther nonsense after the nomination was decided.”

Despite the seemingly slow start for congressional campaign spending, consultants from both sides of the aisle believe this cycle will see a boom in advertising for House and Senate races, and the money spent by the outside groups will end up boosting the total, rather than replacing candidate spending.

Already, in races where super PACs haven't been spending big, campaigns are. One example: The dead-even Massachusetts Senate race between former White House financial reform adviser Elizabeth Warren and Republican Scott Brown, the surprise 2010 winner of the special election for the seat occupied for more than four decades by the late liberal Democratic icon, Sen. Ted Kennedy. Facing a charismatic incumbent, along with a recent controversy over her claim of native American lineage, Warren has already stepped up the ad buy, spending more than $1.66 million so far. By contrast, Brown has spent $227,235 on advertising.

Big fundraisers like Warren (she's brought in $15 million so far for her campaign–the average Senate challenger has raised less than $700,000 at this point, according to the Center for Responsive Politics) will have to spend their own money on media. The help she's gotten so far far from outside groups has been minimal: Liberal groups have spent about $170,000, mostly on negative online ads against Brown.

Of course, the biggest spending will start after Labor Day, when the general election takes off. Campaigns strategists say that one factor likely to drive the big ad spending is that super PACs have made ad spots more expensive and created more competitors vying for the same time slots in various TV and radio markets.

“In some cases Super PACs and campaigns are competing against each other for the same inventory, the law of supply and demand dictates the costs will increase for everyone," said Dan Allen, GOP campaign strategist with Scott Howell and Co.

For this analysis, the Sunlight Reporting Group looked at campaign spending disclosures filed with the Federal Election Commission for the 2012 cycle, including pre-primary reports submitted, until mid-May. Terms such as advertising and media were used as search terms to identify spending criteria.

Table 1: All super PAC expenditures by race