Those attack ads are courtesy of . . . who knows?

The state’s general election is less than three months away, so you know what that means: Get your thumb in shape for working the remote control’s channel changer. You’re going to want to miss a lot of nasty attack ads.

The worst are the third-party ads – the ones that don’t have a candidate saying “I’m so and so, and I approved this message.” Even if you pay close attention, you might not be able to figure out who’s behind these ads.

And that’s the point. The big money special interests paying for them don’t want you to know who they are. They figure you might be a little skeptical if you knew the ads were paid for by (insert one or more of the following): drug companies, trial lawyers, Wall Street hedge fund companies, unions . . . you get the drift.

So they contribute to a cover group like the conservative American Action Network, which is behind the infamous “tennis shoes” attack ad slamming Sen. Patty Murray. That ad was recently dissected by FactCheck.org – which investigates the accuracy of what is said by major U.S. political players in advertising, debates, speeches, interviews and news releases.

FactCheck found that the ad makes some damning charges against Murray – accusing her of abusing families and children, for instance – but provides no support for its claims. Instead, the ad refers people to the AAN’s website. There, the group also criticizes Murray for voting in favor of expanding health insurance to millions of children – even though the AAN’s CEO, Republican Norm Coleman, voted the same way when he was in the Senate.

The “tennis shoes” ad is likely the first of many such third-party ads this election cycle, and they’re employed by supporters of both parties. The U.S. Supreme Court ruled earlier this year that corporations and unions can spend as much as they want on independent political advertising.

That wouldn’t be so bad if the voters could find out, in real time, who’s paying for the hits. But in a party-line vote last week, Senate Republicans defeated a bill – the Disclose Act – which would have required that the names of the top five contributors be disclosed. Democrats even tried to buy votes by giving the National Rifle Association an exemption from the disclosure requirement – to no avail.

Until Congress grows a spine and passes meaningful disclosure legislation, Americans will continue to be bombarded by attack ads funded by special interests who are able to keep their identities secret. The best advice to voters: Be skeptical of any claims made in advertising that does not disclose exactly who is behind it.