The Wall Street Journal brings an apple to the orange convention, writing that, “The American Federation of State, County and Municipal Employees is now the biggest outside spender of the 2010 elections, thanks to an 11th-hour effort to boost Democrats that has vaulted the public-sector union ahead of the U.S. Chamber of Commerce, the AFL-CIO and a flock of new Republican groups in campaign spending.”

They may well end up being the top spender, but our data currently puts them at number 8, having spent a more modest $9.6 million–significantly less than the $87.5 million the Journal reports. The New York Times, meanwhile, reports that the top spender among non-party committees is the U.S. Chamber of Commerce at $21.1 million–very close to our own figure of $23.6 million (which, in fairness to the Times, is a constantly rising number). Why the discrepancy between the Journal’s figures and those that Times and we put out?

The Journal got its $87.5 million figure directly from AFSCME, and also got political spending totals from the U.S. Chamber of Commerce, Service Employees International Union and other groups. The Sunlight Foundation is totaling spending reported to the Federal Election Commission.

The disparities between what groups say they are planning to spend and what they’ve reported spending are troubling, to say the least. It’s one of the reasons that we in the Reporting Group use formulations like “U.S. Chamber of Commerce reports spending $29.2 million on lobbying (which includes a wide range of political activities) in the third quarter of 2010,” rather than saying “the Chamber of Commerce spent…”

Some time in 2011, we’ll get more complete annual reports from the labor unions which dislcose their political spending, forms 990 from groups like the U.S. Chamber of Commerce, year end reports from 527 organizations, and from this information we will begin to piece together how much was spent on the mid-term elections. Even then, it can be daunting.

Lets take a look at one organization: The U.S. Chamber of Commerce disclosed, in the 2008 form 990 it filed with the Internal Revenue Service, spending $23 million of election-related spending and another $4.7 million lobbying. It reported spending $16.5 on electioneering communications to the Federal Election Commission. The Chamber also disclosed to the House and Senate in 2008 that it spent $62 million on lobbying–defined as influencing legislation; participating in any political campaign, including state and local races; attempting to influence the public to on political matters or elections as well as contacts with certain high ranking executive branch officials. Its affiliates spent about $31 million more. Which is the right number?

It might seem like we are mixing apples, oranges and xylophones here (FEC, IRS and lobbying disclosures), but remember, we’re trying to get a handle on who spends the most on political activity. The IRS lobbying definition the Chamber uses when it files lobbying reports with Congress doesn’t produce a number that matches the two, separate numbers it reports to Internal Revenue Service or those two numbers added to the FEC number–16.5 + 4.7 + 23 does not equal 62 (being a journalist, I’ve counted it out on my fingers twice to make sure). This doesn’t mean that any of these individual numbers is wrong or inaccurate (although I suspect all of them are to some degree)–just that they report different things.

In the case of the Chamber, the lobbying disclosure form filed with the House and Senate comes closest to capturing total spending but offers no itemization. For labor unions, it’s the annual report–form LM2–they file with the Labor Department, which unlike lobbying disclosure forms actually itemize expenses.

So while one should treat the Wall Street Journal’s numbers with a bit of skepticism–consider the source–it’s not crazy to ask these groups what they’re spending. I’m not sure I’d be comfortable saying that AFSCME has leapt into first place on their say-so, but one should also be careful to recognize that disclosure from the Federal Election Commission is by no means all-inclusive. For example, no U.S. Chamber of Commerce ad that ran more than 30 days before a primary or more than 60 days before the general election had to be disclosed anywhere–except to the local TV, radio or cable operator that ran it. But that’s because Federal Communications Commission rules require that disclosure, not federal election law.

And to answer the question in the headline honestly, we’d have to say that at this point we just don’t know. According to the FEC, it’s the Chamber. According the groups themselves, it’s AFSCME. All we do know is what they are required to report to the FEC, which is the only tool we have right now for tracking outside spending.