• by Joe Mandese  @mp_joemandese, May 3, 2011

Dave Thomas, a long-time Nielsen Co. executive who helped cable networks develop the kind of research data that have made them a bigger part of the TV ratings business than broadcast networks, is stepping down next month and will be replaced by another long-time Nielsen executive, Mitch Barns, whom some see as a potential heir to Nielsen chief David Calhoun.

Barns, who is currently president of Nielsen Greater China, and has overseen the research giant's move into the burgeoning Asian marketplace, will replace Thomas as president of media client services, the division that includes Nielsen's TV ratings business, on June 1.

Thomas, who participated in not one, but two Nielsen public stock offerings, is not believed to be leaving Nielsen for another job immediately, but is expected to take time off from the business before taking on another industry role. Before joining Nielsen in the 1980s, Thomas was a long-time Madison Avenue executive who began his career at legendary agency Cunningham & Walsh, and worked at DeWitt Media (now Publicis' Optimedia) before joining Nielsen.

Early in his Nielsen career he helped get struggling cable networks "on the plan" by developing important research products like the cable industry's National Audience Demographics reports, which helped them position the underlying value of their audience composition vis a vis the higher overall ratings of the broadcast networks. Currently, cable networks are a greater source of revenues for Nielsen than the major broadcast networks are.

Thomas also was a key player inside Nielsen resolving a war that broke out with News Corp. over ratings methods for minority TV audiences that the media giant believed hurt its Fox network and station group. Fox turned that battle into a political tussle, leveraging social and consumer advocacy groups to get Congressional hearings on the subject, and influenced the way Nielsen measures and "weights" the TV viewing population. The conflict resolved with a giant, long-term contract between Nielsen and News Corp. that is estimated to be worth nearly $1 billion, making it one of Nielsen's biggest deals ever.

Thomas was also a key player in long-term contracts with other big Nielsen clients, including Time Warner and NBC Universal.