Indeed, much of the money being injected into the special election comes from politically active nonprofits that aren't required to publicly disclose their donors as candidates, party committees and super PACs must.
Jolly’s campaign alone has been aided by nonprofits such as the U.S. Chamber of Commerce, the American Action Network and the YG Network. Together these nonprofits have spent about $1.9 million on ads, FEC records indicate, including $1.2 million from the Chamber.
While the deep-pocketed trade association does not disclose its funders — and has actively lobbied against stricter disclosure rules — numerous Fortune 500 companies, including Chevron, Dow Chemical and Merck, have voluntarily self-reported contributions to the Chamber, as the Center for Public Integrity previously reported.
Meanwhile, the American Action Network — which is led by former GOP Sen. Norm Coleman — has received financial support in recent years from other nonprofits such as the American Petroleum Institute, the Motion Picture Association of America and the Republican Jewish Coalition, according to research by the Center for Responsive Politics.
It has also previously been backed by the Pharmaceutical Research and Manufacturers of America and by Exelon, the Chicago-based company that operates the nation’s largest commercial nuclear fleet.
No donors to the YG Network — a nonprofit run by former aides of House Majority Leader Eric Cantor, R-Va. — are publicly known.
In all, outside groups supporting Jolly have spent more than $4.9 million on political ads. Roughly 84 percent of this spending has been critical of Sink.
The National Republican Congressional Committee accounted for about $2.2 million of this sum.
Another large spender has been the pro-Republican super PAC American Crossroads, which was co-founded by party strategists Karl Rove and Ed Gillespie, spending about $470,000.
All the while, Democratic-aligned groups, including the Democratic Congressional Campaign Committee and several left-leaning super PACs, have pummeled Jolly. These organizations have spent about $3.7 million, of which about 95 percent went toward anti-Jolly ads.
The DCCC accounted for nearly 60 percent of that amount, while the House Majority PAC has spent about $956,000. One nonprofit — the National Jewish Democratic Council — has reported spending about $9,200 on Sink’s behalf in the race.
For her part, Sink, Florida’s former chief financial officer, has raised about $2.7 million, according to FEC records, while Jolly, a former congressional aide-turned-lobbyist, has raised more than $1.2 million.
Florida's special election is the latest example of outside organizations' growing clout in congressional races.
During the 2010 election cycle, party committees, super PACs and nonprofits outgunned the candidates themselves in a dozen House races, according to data provided to the Center for Public Integrity by the Center for Responsive Politics. The phenomenon was repeated two years later in more than two dozen House races.
The big-dollar Florida election is being conducted to replace Republican Rep. Bill Young, who died in October.
President Barack Obama bested Republican Mitt Romney in the district by one percentage point in 2012, according to the Cook Political Report, which ranks the contest as a toss-up.