The Federal Communications Commission approved new regulations Friday requiring broadcasters to publish political advertising data online, a move that could shed light on who is trying to influence elections amid unprecedented campaign spending.

Television stations already are required to track purchases of political advertising and make the information publicly available, but posting it on the Web will make it easier to access. Only stations affiliated with ABC, NBC, CBS and Fox in the top 50 media markets will be required to post data on new ad buys this year, with smaller stations expected to follow in 2014.

The FCC estimated that the rule would lead to the disclosure of $3.2 billion in political spending this election cycle, while compliance costs for stations would be less than $400 apiece. Chairman Julius Genachowski said the benefit to the public outweighs any burden to stations.

“I call it common sense,” he said. “It fulfills the core intent of the public file rules, to provide the public access to information.” Genachowski added that the broadcaster requirements are part of an ongoing effort at the agency to move disclosure information online.

To demonstrate the difficulty of accessing broadcaster files under the current system, Genachowski said that FCC staff spent 61 hours and $1,700 in copying costs trying to collect political advertising data from stations in Baltimore.

“Congress explicitly requires broadcasters to disclose this information to the public,” he said.

Republican Commissioner Robert M. McDowell dissented, saying that compliance costs for stations could run much higher than the agency has estimated. He said stations would have to divert tens of thousands of dollars in resources to keep ad data updated during a busy election season. Broadcasters have made similar arguments.

“The majority cannot be sure if it is doing more harm to the public interest than good,” he said.

McDowell recommended that Congress should focus on disclosure from political spenders themselves, rather than requiring more information from broadcasters, who comprise “one of many, many recipients.”

Some Members have pressed for the FCC to use its authority over broadcasters to help reveal who is spending money on political ads in the aftermath of the Supreme Court decision that allowed unlimited corporate spending on elections.

Rep. Anna Eshoo (D-Calif.) said before today’s FCC decision that online disclosure is a necessary step in the digital era.

“Why should [disclosure reports] just sit in some file somewhere,” asked Eshoo, the ranking member on the Energy and Commerce Subcommittee on Communications and Technology. She called resistance by broadcasters “laughable.”

“I have my needle stuck on this,” she added. “You’re going to see whatever opportunities there are in the committee I’m on and its jurisdictions, as well as other areas, to really press hard for disclosure.”

Rep. Lee Terry (R-Neb.) also a member of that subcommittee, said that the Federal Election Commission, not the FCC, should make decisions about political campaigns.

“This is where the FCC starts getting into politics,” Terry said Thursday. “I don’t think that’s appropriate to put that level of burden. It’s already made public.”

Broadcasters also have argued that compliance would reveal proprietary pricing data to competitors.

The National Association of Broadcasters cautioned that stations spend hundreds of thousands of dollars maintaining public files in busy political seasons.

“We’re disappointed that the commission rejected compromise proposals proffered by broadcasters,” NAB spokesman Dennis Wharton said in a statement. “By forcing broadcasters to be the only medium to disclose on the Internet our political advertising rates, the FCC jeopardizes the competitive standing of stations.”

The rule also faced criticism from good-government groups that favor disclosure. The Sunlight Foundation said the FCC should not have exempted some media markets, because smaller news channels in key battleground states could air a considerable number of political ads.

“Many large markets, which charge the highest advertising rates, can have relatively little election-related advertising,” Sunlight spokeswoman Liz Bartolomeo said in a written statement.

A version of this story originally appeared on CQ.com