This month, just before the Pennsylvania primary, Mitt Romney’s campaign bought a 30-second commercial on CBS-owned KYW-TV Philadelphia that ran during the station’s late local news. The ad cost $1,800.

That’s hardly confidential information. The details of such political advertising purchases are available to anybody willing to schlep to their local television station and ask to see the public files.

But now the Federal Communications Commission wants to take that same material, which is required by law to be made available to the public, out of a dusty filing cabinet and onto the Internet. On Friday, the FCC will vote on whether to make that a new rule.

Broadcasters are crying foul. Even though that information is already technically public, they fear putting that level of detail on the Web will undermine their own businesses.

“One poker player would, in effect, have had at least a partial glance at the other’s hand,” broadcast networks CBS, NBC, ABC, Fox and Univision wrote in comments filed at the regulatory agency.

By law, in the weeks leading up to a primary or general election, broadcasters are required to sell candidates ad time at the lowest rate paid by a commercial business in that same show or time of day. (Commercial rates fluctuate on a weekly and sometimes daily basis.)

The concern among TV station owners is that commercial advertisers will use the detailed information about rates as leverage in their own negotiations. There is also fear that one station could learn what another is charging and then undercut its rates with advertisers.

In some cases, the rates are very low. In February the Obama for America campaign paid $250 for a 30-second spot on WWJ-TV Detroit.

Alan Frank, president of Post-Newsweek Stations, which has TV outlets in several big cities, including Detroit and Miami, said the FCC’s plan is full of “unintended consequences.” He added that the industry is fine with the online publication of the rates that candidates and political action committees spent on ads with their stations. But they don’t want to get into the fine print of what ads on specific shows cost.

Under the current system, visitors who want to study political ad sales must visit the TV station in person, and then wade through reams of paperwork to find whatever factual nugget they seek. The process is labor-intensive and time-consuming — especially compared with the ease of doing a document search over the Internet.

The broadcasters like that, figuring it makes rival stations and advertisers reluctant to comb through files looking for inside information on advertising rates.

“It is a fundamentally different thing when you keep it in your station versus putting it online,” said Gordon Smith, president of the National Assn. of Broadcasters, the television industry’s chief lobbying arm.

Some have also expressed concern that making the information more easily available could run afoul of antitrust law.

“If government authorities would look askance, as they surely would, at sales executives from competing television stations gathering in a conference room to share this information, why would the government require that the same information be made so easily accessible online?” the big networks asked in comments to the FCC.

FCC Chairman Julius Genachowski sees it differently. Last week, in a speech at the National Assn. of Broadcasters convention, he delivered a stinging rebuke to those in the television industry resisting the commission’s proposals, saying they are “against technology, against transparency and against journalism.”

Media watchdogs and academics also think the broadcasters are overreacting. Andrew Schwartzman, senior vice president of the Media Access Project, said it is ironic that “broadcasters, who as journalists advocate for freedom of information laws, now want secrecy when it comes to their own operations.”

J. Adam Skaggs, senior counsel at the Brennan Center for Justice, said greater disclosure of the actual rates would help ensure broadcasters are following the lowest-unit rate rules.

As for the worries of exposing sensitive pricing information to advertisers and rival stations every election cycle, Schwartzman said, “If it is leveling the playing field a little bit, that is part of the price broadcasters have to pay for getting a free license.”

Although Genachowski appears to have the votes to push the rule change through, broadcast executives and lobbyists have been barraging the FCC with pleas to keep the commercial rate information off the Web.

“It’s fair to say people on our side are very nervous,” Schwartzman said. “The broadcasters have taken what to us seemed like a fairly minor issue and turned it into a major confrontation.”

But that may just be lobbyists earning their paychecks. The National Assn. of Broadcasters’ Smith seemed resigned that Genachowski would get his way on the issue.

“Who can be against Mom, apple pie and the American way of transparency?” he cracked.

joe.flint@latimes.com