SHOULD Barack Obama win the presidency and Democrats take full control of Congress, next year will see a real legislative attempt to bring back the Fairness Doctrine - and to diminish conservatives' influence on broadcast radio, the one medium they dominate.

Yes, the Obama campaign said some months back that the candidate doesn't seek to re-impose this regulation, which, until Ronald Reagan's FCC phased it out in the 1980s, required TV and radio broadcasters to give balanced airtime to opposing viewpoints or face steep fines or even loss of license. But most Democrats - including party elders Nancy Pelosi, John Kerry and Al Gore - strongly support the idea of mandating "fairness."

The Fairness Doctrine was an astonishingly bad idea. It's a too-tempting power for government to abuse. When the doctrine was in effect, both Democratic and Republican administrations regularly used it to harass critics on radio and TV.

Second, a new Fairness Doctrine would drive political talk radio off the dial. If a station ran a big-audience conservative program like, say, Laura Ingraham's, it would also have to run a left-leaning alternative. But liberals don't do well on talk radio, as the failure of Air America and indeed all other liberal efforts in the medium to date show. Stations would likely trim back conservative shows so as to avoid airing unsuccessful liberal ones.

Then there's all the lawyers you'd have to hire to respond to the regulators measuring how much time you devoted to this topic or that. Too much risk and hassle, many radio executives would conclude. Why not switch formats to something less charged - like entertainment or sports coverage?

For those who dismiss this threat to freedom of the airwaves as unlikely, consider how the politics of "fairness" might play out with the public. A Rasmussen poll last summer found that fully 47 percent of respondents backed the idea of requiring radio and television stations to offer "equal amounts of conservative and liberal political commentary," with 39 percent opposed.

Liberals, Rasmussen found, support a Fairness Doctrine by 54 percent to 26 percent, while Republicans and unaffiliated voters were more evenly divided. The language of "fairness" is seductive.

Even with control of Washington and public support, Dems would have a big fight in passing a Fairness Doctrine. Rush Limbaugh & Co. wouldn't sit by idly and let themselves be regulated into silence, making the outcome of any battle uncertain. But Obama and the Democrats also plan other, more subtle regulations that would achieve much the same outcome.

He and most Democrats want to expand broadcasters' public-interest duties. One such measure would be to impose greater "local accountability" on them - requiring stations to carry more local programming whether the public wants it or not. The reform would entail setting up community boards to make their demands known when station licenses come up for renewal. The measure is clearly aimed at national syndicators like Clear Channel that offer conservative shows. It's a Fairness Doctrine by subterfuge.

Obama also wants to relicense stations every two years (not eight, as is the case now), so these monitors would be a constant worry for stations. Finally, the Democrats also want more minority-owned stations and plan to intervene in the radio marketplace to ensure that outcome.

It's worth noting, as Jesse Walker does in the latest Reason magazine, that Trinity Church, the controversial church Obama attended for many years, is heavily involved in the media-reform movement, having sought to restore the Fairness Doctrine, prevent media consolidation and deny licenses to stations that refuse to carry enough children's programming.

Regrettably, media freedom hasn't been made an issue by the McCain campaign, perhaps because the maverick senator is himself no fan of unbridled political speech, as his long support of aggressive campaign-finance regulation underscores. But the threat to free speech is real - and profoundly disturbing.