The Federal Communications Commission is scheduled to vote April 27 on whether to require TV stations to post online public information about political ad buys. Some form of the rule seems likely to pass, but the industry and others are lobbying the FCC to alter the nature of the final rule.

(With the help of readers around the country, ProPublica is collecting stations’ public paper files containing data on political ads and posting them online because the information is generally unavailable elsewhere. See “Free the Files.”)

Right now we only know the broad thrust the proposed FCC rule: That broadcasters would have to electronically send the commission updates to its political file — in other words, information about what political ads are being purchased, by whom, and for how much money — instead of merely maintaining paper files at the stations, the current practice. The information would be made public on an FCC website.

The rule would apply initially to affiliates of the four major networks — ABC, CBS, NBC and FOX — in the top 50 markets. All other stations would have another two years before they'd have to begin filing electronically.

But the FCC won’t release the exact text of the rule until after the panel votes to finalize it later this month. Meanwhile, the wording is subject to change based on input from interested parties.

That’s why the National Association of Broadcasters has been paying visits to key FCC ...