Was it worth it? That’s what members and supporters of the U.S. Chamber of Commerce should ask themselves after the revelation that the national business group’s political arm was the sole funding source behind the shadowy ad campaign against Deborah Senn, a candidate for attorney general in Washington state.

Don Brunell, president of The Association of Washington Business, a state affiliate to the U.S. Chamber, said he was left in the dark until Friday evening, and he didn’t seem too pleased.

“I guess I’m disappointed,” Brunell told the Seattle Times, adding, “I would hope that if something is going to be some project … in Washington state, there’d be some kind of collaboration. … We’re trying to figure out what’s happening. It forces us to distance ourselves from a good partner.”

Rich Hadley, president of the Spokane Regional Chamber of Commerce, also distanced his organization from the national effort. “We don’t agree with negative ads and attempts to circumvent the public disclosure process,” he wrote for the local chamber’s Web site.

To recap: A group called the Voters Education Committee spent $586,000 on a slew of ads that criticized some of Senn’s activities when she was the state’s insurance commissioner. The Public Disclosure Commission, the state’s campaign finance watchdog, said the ads qualified as political advocacy and requested disclosure of the ad’s financial backers. The Voters Education Committee argued – implausibly – that the ads were issue-oriented and were not designed to sway voters, therefore it was not required to disclose its backers. The PDC then turned the case over to the attorney general’s office, which sued to force disclosure.

Senn’s tenure as insurance commissioner was controversial, and we were critical of her overly aggressive posture toward insurance companies. So that was legitimate grounds for criticism, but what we don’t understand is why the U.S. chamber’s Institute for Legal Reform chose to conceal itself. In doing so, the issue became the secret accuser rather than the message. And in the end, the U.S. chamber, not Senn, walked away with a black eye.

The U.S. chamber says that the anti-Senn ad is part of a national effort to defeat attorney general and supreme court candidates in 25 races nationwide. But the group doesn’t always go under the radar, and it’s still not clear why it felt the need to do so in Washington state. An official said the organization thought the ad would be more credible if it were presented by a local group. He couldn’t have been more wrong.

Few people had ever heard of the Voters Education Committee, and the anonymity of the accusers cast doubt on their claims. Additionally, the mystery set off speculation that other candidates in the race were involved. By the time the attackers were revealed, a large percentage of voters had already cast their ballots, and the others had little time to digest the new information. In short, it was unfair to all involved.

We hope the attorney general’s office pursues civil penalties in the case to send a message to future plotters of shadowy campaigns: The state of Washington takes the issue of campaign-finance disclosure very seriously, and efforts to skirt the law won’t be worth it.