Once read for the most part only by Washington politicos, beltway publications like the recently launched The Politico and old-timers The Hill and Roll Call are now attracting online readers from all over the country - and advertisers such as advocacy groups and corporations are following suit, reports ClickZ.

Online, corporations and advocacy groups can reach not only those casting votes on the floor of the House or Senate when legislation affecting them is up for vote but also the people voting in presidential caucuses and primaries.

For example, The Alaska Wilderness League launched ads on The Politico to promote its Climate Crisis Action Day to be held in D.C. The group hopes to raise awareness about the event among beltway insiders as well as environmental activists around the country.

Beltway publications are "the equivalent of national sports pages," said Dan Solomon, CEO of Mindshare Interactive Campaigns. "Their outside-the-beltway influence is one of the hidden gems."