The two Democrats on the commission, Genachowski and Mignon Clyburn, have expressed support for the proposal but Republican Commissioner Robert McDowell has criticized it.
Broadcasters are already required to keep records on political spending on advertising, but the proposed rule would require that the stations load the information onto an online database.
Watchdog groups hope the rules will shed light on the big money behind political ad campaigns by making the data more accessible. The 2012 election could see an explosion of outside spending from SuperPAC groups.
"While technical limitations might have made widespread availability of the public file infeasible in 1950, the failure to do so in 2012 — using the Internet — is inexcusable," Eshoo wrote.
But broadcasters say the proposed rule would be burdensome to stations. They also argue it is unfair to impose requirements on broadcast television but not their competitors in cable and satellite.
A group of Republican senators urged Genachowski to abandon the proposal in a letter earlier this month. They called the rule "excessive and unnecessary" and said it would impose "heavy compliance costs."
The latest version of the regulation would only apply to network-affiliated stations in the top 50 markets for the first two years. After that period, all stations would have to comply with the requirements.
Genachowski has said the proposal is part of the commission's effort to increase transparency and put more information online. He said the proposed rule would allow academics, journalists and members of the general public to more easily find out which groups are buying political ads and how much they're spending.