Businesses have given more than $33 million to super PACs since the beginning of this campaign cycle, according to a Sunlight analysis of campaign finance reports. Trade unions gave at least $15 million in the same time period.

Republican-aligned super PACs got the lion's share of business contributions, taking in just under $30 million. That dwarfed the $3.8 million that their Democratic-leaning counterparts received from business. Yet the gap may be narrowing ahead of the general election: Left-leaning super PACs raised almost $1.2 million from business in June, while super PACs siding with the GOP raised $4.5 million. 

Sunlight's analysis examined the $61.8 million in organizations' contributions to super PACs from the beginning of last year through the end of June. We categorized donations of $10,000 or more as coming from:

• Businesses;
• Labor unions and allied labor groups;
• Family trusts;
• Native American tribes;
• Trade associations
• Other political groups, including nonprofit "social welfare" organizations

The analysis generally left out transfers from other political committees, which are reported in another section of the campaign finance reports. (For more about how we categorized super PACs' political allegiances, read the methodology.)

Political groups' donations came to $5.7 million, trade groups gave $2.6 million (though nearly all the money went to super PACs unaligned with any party), family trusts $2.4 million and Native American tribes $343,000. Uncategorized donations of less than $10,000 came to $1.5 million. The complete organizational donor files in the analysis, which includes the designations assigned to each gift, is available for download.

Table 1. Organizational contributions to super PAC by party affiliation and donor type

The $33 million that businesses contributed to super PACs likely represents a fraction of their efforts to influence the outcome of the November elections. That's because donations to super PACs are just one avenue for corporations and labor unions to give to groups trying to sway the results of this year's elections, and for many it is the least attractive option.

Businesses that want to avoid alienating customers of a different political persuasion have less transparent alternatives: Donations to non-profit political groups that claim to be "social welfare organizations" do not require disclosure. And less attention has been paid of late to so-called "527 organizations," which can accept donations of any size but must report their donors to the IRS. The biggest of these, the Republican Governor's Association, raised more than $38 million from business groups between the start of 2011 and March 31 of this year.

While it's common for well-known and publicly traded companies to donate to 527 groups, like the Republican Governor's Association, they've been shyer about giving to super PACs, perhaps fearing a public backlash. But a number of well-known brands have given to GOP-allied super PACs including Waffle House ($100,000 to American Crossroads), 7-Eleven ($25,000 to Hoosiers for Jobs), White Castle ($25,000 to the Congressional Leadership Fund) and Borden Dairy Company ($25,000 to Congressional Leadership Fund). There are also publicly-traded companies: Scotts Miracle-Gro Company(NYSE: SMG), Consol Energy Inc.(NYSE: CNX), Alpha Natural Resources (NYSE: ANR), Chesapeake Energy (NYSE: CHK) and SCI International (NYSE: SCI), which bills itself as "North America’s largest single provider of funeral, cremation and cemetery services" via SCI Executives, Inc. and SCI Executive Services, Inc.

There's no comparable set of businesses donating to left-leaning super PACs, but Working Assets, a phone service affiliated with CREDO mobile that bills itself as donating to "progressive" causes, has given over $440,000 to Credo super PAC.

The biggest union donors are familiar names, and have given exclusively to left-leaning super PACs: the National Education Association ($5.1 million), the AFL-CIO ($2.2 million), Communications Workers of America ($1.7 million) and the American Federation of State, County & Municipal Employees ($1.4 million).

The most significant business donors aren't as well-known. Contran Corporation has given $3 million (it is owned by Harold Simmons, a Dallas billlionaire who's also given heavily); Crow Holdings ($2.45 million), associated with construction giant Trammell Crow; Oxbow Carbon ($1.75 million), lead by Bill Koch, brother of better-known billionaire industrialists and right-wing philanthropists Charles and David Koch.

Oxbow Carbon's contributions, however, are surpassed by the $2.25 million given by four companies led by Robert T. Brockman: Waterbury Properties, L.L.C., CRC Information Systems, Inc., Fairbanks Properties, L.L.C., and Dealer Computer Services, Inc. The beneficiaries of the Brockman concerns' largesse are four super PACs that support GOP candidates:  Restore Our Future ($1 million), American Crossroads ($1 million), the Texas Conservatives Fund ($200,000) and Restoring Prosperity Fund ($50,000).