Bandow told BusinessWeek Online that he had accepted money from Abramoff for writing between 12 and 24 articles over a period of years, beginning in the mid '90s, with many payments at $2000 a column.

"It was a lapse of judgment on my part, and I take full responsibility for it," Bandow said. A Cato spokesman told E&P that his tainted articles were being "scrubbed" from its Web site.

Abramoff also paid a second think-tanker, Peter Ferrara, a senior policy adviser at the conservative Institute for Policy Innovation who had a high profile in the recent Social Security debate.

Bandow did not disclose any Abramoff payments in any of his columns, or by Cato. Copley News Service did not immediately respond to inquiries about the future of Bandow's columns.

In an early reaction, Marty Kaplan, associate dean of the USC Annenberg School for Communication, wrote at the Huffington Post blog today, "Move over, Armstrong Williams. Step aside, Maggie Gallagher. The gasbags-for-rent business has just gotten more competitive."

For years, "rumors have swirled of an underground opinion 'pay-for-play' industry in Washington in which think-tank employees and pundits trade their ability to shape public perception for cash," Business Week observed.

Neither Ferrara, nor Tom Giovanetti, president of the Institute for Policy Innovation, expressed any ethical qualms about the pay-for-play. Giovanetti said critics are applying a "naive purity standard" to the op-ed business, adding, "I have a sense that there are a lot of people at think tanks who have similar arrangements."

Cato Communications Director Jamie Dettmer said the think-tank determined that Bandow "engaged in what we consider to be inappropriate behavior" and accepted his resignation.

Bandow confirmed receiving $2,000 for some pieces, but said it was "usually less than that amount." He added that he wrote all the pieces himself -- but with topics and information provided by Abramoff. He said he wouldn't write about subjects that didn't interest him.

Bandow wrote favorably about Abramoff's Indian tribal clients -- as well as another Abramoff client, the Commonwealth of the Northern Mariana Islands -- as far back as 1997. One Copley column saluted a Abramoff client tribe, the Mississippi Choctaws, for their entrepreneurial spirit, hard work, and commitment to free enterprise. "The Choctaws offer a model for other tribes," Bandow wrote.

He also wrote: "The BIA [Bureau of Indian Affairs] seems intent on keeping native Americans dependent. Still, critics will be more effective if they not only decry BIA inefficiency, but also help point the way to tribal independence. And the best way to do this is to highlight Indian entrepreneurship."

Dettmer told E&P, "We will be removing some articles in archives Doug wrote in connection with Indian tribes," about 12 to two dozen in all, with help from Bandow to identify them. His name has already been deleted in the "fellows" section of the Cato site. "We reacted promptly and speedily," Dettmer added, "we take the integrity of our institution very seriously....We considered Doug’s actions were inappropriate...He’s paid a very high price and we’ve lost a very good friend.”