Last week, for example, the group spent $362,000 on a television ad attacking Steve Southerland, the Republican challenger to Representative Allen Boyd, Democrat of Florida. But the 60 Plus Association, a nonprofit advocacy group that bills itself as a conservative alternative to AARP, began attacking the Democratic incumbent on television as early as late August.
In the closing stretch of the campaign, Democratic candidates in competitive races generally have had more money in the bank to spend than their Republican counterparts. As of Oct. 13, Democrats in House races in play collectively had about $45 million in cash on hand, compared with about $32. million for Republicans.
In contest after contest, however, Democratic candidates with huge financial advantages over underfinanced Republican opponents have found themselves under siege.
Outside group spending has already far exceeded the total for the last midterm election cycle, in 2006, and is on track to surpass even what was spent by independent groups in 2008, a presidential election year, according to data from the Center for Responsive Politics.
The hand-to-hand political combat between candidates, who must inch along in their own fund-raising in relatively modest bites, and these groups, which are able to leapfrog ahead with the help of a single giant donation, casts in bold relief the kind of outsized influence corporate and individual megadonors to such organizations can exert on specific races.
Take, for example, the tight race in New York’s 20th Congressional District. Representative Scott Murphy, a Democrat who was elected in 2009 to replace Kirsten Gillibrand, after she ascended to the Senate, has spent $1.5 million since late August, compared with less than $400,000 by his Republican challenger, Chris Gibson, a retired Army colonel.
But Mr. Gibson has been helped by more than $700,000 in spending by Republican-leaning outside groups, while Democratic-leaning groups have spent less than $200,000 supporting Mr. Murphy.
American Crossroads, one of a pair of independent groups tied to Karl Rove, spent about $200,000 in mid-October on a television commercial attacking Mr. Murphy for his support of the health care overhaul.
The group’s most recent filings with the election commission revealed $14.7 million in donations since September, two-thirds of which essentially came from two people, Bob Perry, a Houston home builder, and Robert B. Rowling, a billionaire from Dallas.
Leading the way in independent group spending on House races has been the U.S. Chamber of Commerce, which has reported spending more than $12 million on “issue ads” in House races dating back to September, mostly attacking Democratic candidates.
Other top-spending Republican-oriented groups in House races include: American Action Network, a nonprofit advocacy group created this year by Republican operatives, which has reported spending about $10 million; the 60 Plus Association has disclosed expenditures of roughly $8 million; and American Future Fund, an Iowa-based nonprofit, has reported investing about $7 million in House races.
At over $5 million, the American Federation of State, County and Municipal Employees, a labor union, has been the biggest outside group spender on the Democratic side, followed closely by America’s Families First Action Fund, with about $4.8 million.