BOB GARFIELD: We're back with On the Media. I'm Bob Garfield.

BROOKE GLADSTONE: And I'm Brooke Gladstone. If you read your local letters to the editor regularly, you may have seen this heartfelt letter praising the president. It begins with this sentence: "When it comes to the economy, President Bush is demonstrating genuine leadership." And it continues with this: "Contrary to the class warfare rhetoric attacking the president's plan, the proposal helps everyone who pays taxes." Over the last month, the same letter, signed by different people, has appeared in newspapers across the country. It's been dubbed "astroturf" -- something that has the appearance of grassroots sentiment that's actually been manufactured by an interest group. Declan McCullagh, chief political correspondent for CNET's News.com is no stranger to astroturf. His web site, www.politechbot.com, explores the interplay between technology and politics. But McCullagh can't claim credit for finding this latest example of astroturf. He says it was bloggers who grew suspicious, did a Google search with some key phrases from the letter, found them duplicated in letters to the editor coast to coast.

DECLAN McCULLAGH: The letters were actually identical because they were generated by the Republican web site. I found about a dozen or so on my own.

BROOKE GLADSTONE: How is this different from a traditional mass letter-writing campaign? I mean the fact is form letters have been circulating and, and been sent to Congresspeople from time immemorial. Is the big difference here the fact that these form letters are going to newspapers rather than to Congressmen and women?

DECLAN McCULLAGH: I think that's one big difference. The ACLU, for instance, I remember them being one of the first to set up a web site that lets you e-mail and fax members of Congress. It seemed to work pretty well. Whenever there was a big campaign going on they'd fire it up and maybe they had an effect. But some, somehow it seems different to me --maybe it's [LAUGHS] because I'm part of the media -- but it seems different when we're getting messages that we don't necessarily know are coming from a Republican Party e-mail bought rather than individuals who are composing them themselves.

BROOKE GLADSTONE: And what was really sad is that there are a number of papers, like the Detroit News, which published the almost identical letter merely a week apart and didn't seem to pick up on the similar phrasing even then!

DECLAN McCULLAGH: There's [LAUGHS] no excuse for that. You can, you can understand a paper being taken in by letters that seem real, but publishing the identical one there's some institutional knowledge there [LAUGHS] that seems to be lacking.

BROOKE GLADSTONE: Where does most astroturf come from do you think, across the political spectrum?

DECLAN McCULLAGH: I think this is a growth area, and it seems to be a non-partisan [LAUGHS] one. The Republicans might be a little bit more adept at using the web, but the Democratic National Committee site has a way to e-mail pre-written letters to members of Congress. Let me add one more thing, if you don't mind. What the Republicans are doing is a first step towards sort of electronic delegation of our e-mail inboxes. Right now you actually have to affirmatively click and say yes, I want to send a message to my local newspapers. But you can imagine a, a tech-- some technology in the future -- the not-so-distant future -- that has a Republican or Democratic or what-not e-mail bots. You configure it -you tell it your preferences; you go down a list of little checkboxes on their web form and say these are the issues I care about. And then whenever an issue comes up in the media -- whenever a vote is about to happen in Congress, then this intelligent e-mail bought will send out messages -- customized messages -- that you can't even tell were generated by a computer. I talked to a programmer from one political party that asked to remain nameless, and what they're doing is they're generating customized letters -- you, as one of their members, can check off whether you want something to be lighthearted; you want your letter to be angry [LAUGHTER] or sarcastic or polite -- and then it'll pick from a large library of stock paragraphs, arrange them intelligently and then send that one out -- and so it's going to become increasingly difficult for someone in the media [LAUGHS] or even on Capitol Hill to figure out that these are actually computer-generated messages.

BROOKE GLADSTONE: Well sooner or later somebody will be able to track these letters to their sources just as many people tracked the Bush letter to the Republican Party. And there's a term in advertising -- TV advertising -- called "clutter." If you clutter up the political debate with a lot of phony spam letters from people who've merely checked a box and aren't pouring their hearts into these correspondences, then-- they'll cease to become significant. No one will pay attention to them any more.

DECLAN McCULLAGH: Your use of the word "spam" is absolutely correct, because you have the same problem filtering out legitimate e-mail that you actually want to pay attention to from the stuff that's trying to sell you Viagra or something less mentionable. [LAUGHTER] It's the same thing here. How can you tell whether something is a legitimate message or not? Eventually we might have to resort to the time-honored [LAUGHS] method of calling someone on the phone and quizzing them -- hey, is this actually what you thought? What, what did you mean by this wording in the second paragraph.

BROOKE GLADSTONE: [LAUGHS] So this is yet another example of what we frequently say on this program -- Let the reader beware.

DECLAN McCULLAGH: That's right. [LAUGHS] And let the letters-to-the-editor editor beware.

BROOKE GLADSTONE: Well, thank you very much.

DECLAN McCULLAGH: Thank you! You're quite welcome.

BROOKE GLADSTONE: Declan McCullagh is chief political correspondent for CNET's News.com, and he lives and works in Washington, DC. [MUSIC]