If you want to keep up with the inside world of lobbying, I can think of no better tour guide than Jeffrey Birnbaum of the Washington Post. Birnbaum has covered Washington lobbying longer than probably anyone in town – most of it while he was Fortune Magazine’s senior Washington writer – and he understands both the mechanics and culture of K Street, the center of Washington’s lobbying community. His 1986 book “Showdown at Gucci Gulch” remains a classic and his K-Street Confidential column appears every other Monday in the Washington Post.

Today’s installment of the column gives new meaning to an old term – in this case CPA, which in K Street parlance means the “cost per advocate” that interest groups pay to recruit hometown lobbyists through ads on the web.

Yes, the ubiquitous internet, which has given us Google, the blogosphere and paperless newspapers, is also being tapped by interest groups in Washington to find hometown advocates on the cheap.

Lobbyists understand all too well that no one persuades a member of Congress more effectively than someone from their own district, so Washington interest groups have long expended great efforts to find and recruit such people. In the past, this was done by networking with local groups and through direct mail, phone banks and other forms of traditional advertising.  

Birnbaum’s column today takes us inside the Alexandria, VA offices of OnPoint/DDC, one of the companies specializing in linking lobbying firms to the internet.

The first thing you need to know is that the Internet can be watched very closely. OnPoint/DDC’s offices in Old Town are filled with cubicles of computer experts who are in near-constant contact with thousands of display advertisements on Web sites. These experts can see when commercials are clicked on — and when they’re not.

Birnbaum reviews a few of the findings the company has made – text ads work better than fancy pictures, and sarcasm doesn’t work well at all. Then we get to the bottom line:

The AMA hired DDC in 2003 to recruit activists for its then-nascent Patients’ Action Network. On May 19, DDC placed 50 different ads on 7,500 Web sites soliciting people who agreed that Washington should crack down on lawsuits filed against physicians. Six weeks later, it had whittled that down to four ads on 123 sites.

By the end of the six-week program, people were clicking on commercials twice as often on average than they had at the start. Those who did click though, in addition, were five times more likely to sign up as advocates than those who had clicked initially. The C.P.A. was ultimately cut to under $2.

Voila! Lobbying on the cheap.

Birnbaum’s column is a timely reminder – especially after last week’s hoopla about the role of liberal bloggers in defeating Sen. Joe Lieberman in Connecticut – that the web is a neutral medium. It’s not intrinsically Democratic or Republican, or anything else. Like television, radio, the telephone, or any other medium of modern communications, it’s equally useful to “good guys” and “bad guys,” however you may describe those terms.