After Senate Republicans refused to allow a vote on the Disclose Act last night, Senator John McCain sent out a statement explaining his ‘no’ vote. It was two sentences long:

“In its current form, the DISCLOSE Act is closer to a clever attempt at political gamesmanship, than actual reform. By conveniently setting high thresholds for reporting requirements, the DISCLOSE Act forces some entities to inform the public about the origins of their financial support, while allowing others—most notably those affiliated with organized labor – to fly below the Federal Election Commission’s regulatory radar.”

Given that McCain built his alleged maverick persona based in large part on campaign finance reform—when he bucked his party and crafted legislation along with Senator Russ Feingold to reign in soft-money abuses—he had to give some sort of explanation for why he voted against a bill that simply required disclosure from big donors, and was very much in line with even the Citizen’s United decision.

Unfortunately, his explanation doesn’t make much sense.

The bill text says, “Any covered organization that makes campaign-related disbursements aggregating more than $10,000 in an election reporting cycle shall, not later than 24 hours after each disclosure date, file a statement with the Commission made under penalty of perjury” that discloses what expenditures were made and who donated to them.

“Covered organizations” are defined as “Corporations, Labor Organizations, and Certain Other Entities” that expressly advocate for the election or defeat of a clearly identified candidate.

So under that language, any group that hits $10,000 cumulatively in an election disclosure cycle must file a report—whether it’s the Koch-funded Americans for Prosperity or the Service Employees International Union.

In his statement McCain suggests the “high threshold” would allow “organized labor” to fly below the radar, which is hard to parse. (See update below for a look at what McCain means about high thresholds; he elaborated on the Senate floor today.)

Last night on Hardball, Senator Sheldon Whitehouse, who sponsored this version of the Disclose Act and was courting McCain’s support earlier this year, said he was flummoxed by McCain’s rationale.

“In this case, he tells me that there’s something in my bill that favors unions. I don’t see it. It’s $10,000 across the board,” Whitehouse said. “I keep saying, ‘John, tell me what it is and we’ll talk about it,’ and nobody has ever been able to show me what it is.”

UPDATE: Senator McCain took to the Senate floor Tuesday afternoon and delivered a more expansive explanation of his opposition. It deserves a closer look, but is no more convincing than his shorter statement.

McCain charges that two high thresholds in the bill make it easier for unions to conceal their electioneering—the $10,000 individual limit and the $50,000 limit on transfers from affiliates. Both would trigger a disclosure requirement within 24 hours.

He believes these limits are too high, because donations from individual union members and small affiliate organization are unlikely to exceed $10,000 or $50,000, respectively.

He said:

 [T]he local union chapter will not be required to disclose the payments of individual union members to the union, even if those funds will be used for political purposes. What is the final difference between one $10,000 check and 1,000 $10 checks? Other than the impact on trees, very little. So why should one be free from having to disclose its origin? 

The bill exempts from the disclosure requirements transfers from affiliates that do not exceed $50,000 for a two-year election cycle. As a result, unions would not have to disclose the transfers made to it by many of its smaller local chapters. Given the contrast between union and corporate structures, this would allow unions to fall beneath the bill’s threshold limits. For local union chapters, this anonymity is probably very important because, among other effects, it prevents union chapters’ members from learning how much of their dues payments are being used on political activities. […]

It is apparent to me that the unions’ unique, pyramid-style, ground-up money funneling structure, would allow unions to not be treated equally by the DISCLOSE Act. Unlike unions, most organizations do not have thousands of local affiliates where they can pull up to $50,000 in ‘affiliate transfers.’

This is, of course, true—contributions by individual union members or small affiliates are unlikely to show up on union disclosure forms. But the threshold in the bill is set high to snag individual donations or transfers that have the ability to corrupt the political process—and $100 from a steelworker in Pennsylvania is unlikely to do so. As the Sunlight Foundation notes, the same is true with say the Sierra Club or the US Chamber of Commerce—only big donations would be disclosed under this bill, and not those by small donors.

Moreover, it’s hardly a surprise to anyone that union electioneering is funded by union members. Publishing a list of every union member who made a donation doesn’t really advance the cause of transparency, and in fact accomplishes what Senator Mitch McConnell and other prominent conservatives have falsely warned about—that the Disclose Act would force nonprofits to reveal member lists. It won’t, unless McCain successfully tailors the bill to what he described today.

Elsewhere in his speech, McCain notes that unions engage in other sorts of electioneering that wouldn’t be covered by the Disclose Act. He does not mention, however, that unions already must file extensive disclosure forms on virtually all types of political activity. You can view them here.