WASHINGTON — Broadcasters could easily reap $1 billion in political advertising revenues this election season, but the salad days could disappear for good if Capitol Hill approves legislation offered Thursday forcing TV stations to give federal candidates free airtime.

The measure would allow federal candidates and political parties to receive up to $750 million in free ad vouchers, financed by a fee not to exceed 1% of a TV station’s gross annual revenues. It also would require broadcast licenses holders to devote two hours per week to campaign coverage in the weeks preceding an election.

“Today we begin another chapter in the effort to reform our political campaign system,” said Sen. John McCain (R-Ariz.), who co-authored the bill with Sen. Russ Feingold (D-Wis.) and Sen. Richard Durbin (D-Ill.).

“By increasing the flow of political information, free airtime can better inform the public about candidates and invite viewers to become more engaged in their government by learning more about the individuals seeking to represent them,” McCain said.

Feingold and McCain have long railed against the TV biz for not fulfilling its duty to serve the public interest in exchange for getting free use of public airwaves. But their chances of securing passage of the legislation are slim, particularly as Capitol Hill wraps up business before adjourning this weekend for the fall recess.

Study: Sparse coverage

A study released earlier this week by the Norman Lear Center at USC’s Annenberg School and the political science department at the U. of Wisconsin-Madison concluded that viewers are hard-pressed to find news stories on congressional, state and local elections when clicking on their sets–even though the Nov. 5 election is fast-approaching.

An analysis of 2,454 newscasts aired across the country between Sept. 18 and Oct. 4 found that 1,311 shows carried no campaign coverage at all, according to the study.

Broadcasters say they aren’t to blame for the lack of interest in political debate. TV stations report that candidates rarely take advantage of free airtime offered in the weeks leading up to an election.

Almost all TV station groups have offered such time this year.

On top of that, the National Assn. of Broadcasters says TV stations do offer discounted ad rates in many instances. Rates do climb if a candidate wants to secure a non-preemptible, primetime slot.

Earlier this year, McCain and Feingold were forced to abandon their call for broadcasters to offer up free or deeply discounted airtime in order to secure passage of sweeping campaign finance reform legislation. As before, their renewed fight would also force broadcasters to further discount ad rates, in addition to giving the free vouchers.