Here's a quiz for you: Name the best-known and most influential conservative commentators in America? Rush Limbaugh? George F. Will? Bill O'Reilly? Now, quick, who are their liberal counterparts?

If you can't think of any, you're not alone. Conservatives love to rant that liberals dominate the news media. Trouble is, it's just not true. In fact, I'd argue that the biggest problem with America's public discourse today is that the left is barely represented at all on mainstream TV and radio talk shows and in major newspapers and magazines.

To my mind, that's the main reason debate in the U.S. and Europe is diverging so radically on issues ranging from the war in Iraq to genetically engineered food and capital punishment. In, say, London a much more lively debate is going on between the left (given voice in mainstream outlets such as the BBC and Guardian) and the right.

VESTED INTERESTS. The U.S. situation is likely to get a lot worse if Michael Powell, Federal Communications Commission chairman, has his way. He wants to loosen or remove many of the last remaining restrictions on how much of the market Big Media conglomerates can control. Among other things, Powell would allow more cross-ownership of local TV stations and newspapers by the same companies. He also would let a single company own TV stations covering 45% of the national viewing audience, up from 35% now. Powell plans a vote on June 2, and the three-person Republican majority on the commission seems certain to approve the proposed changes.

This isn't good policy. The U.S. needs greater concentration of the media market like a fast-food junkie needs more fat. What we read, hear, and watch is already determined to far too great an extent a half dozen giant conglomerates: AOL Time Warner (AOL ), Viacom (VIA ), Walt Disney (DIS ), News Corp. (NWS ), General Electric (GE ), and Bertelsman. Yet Powell has held just one official public hearing on the proposed changes. And the specifics of the revisions being considered haven't been made public.