From the moment he entered private life, Mr. Gingrich seemed determined to avoid being tagged as a lobbyist, which can be a kiss of death for anyone contemplating a presidential run. An early consulting contract, with a plastics company in 2001, contained language that would become standard: He “does not provide lobbying services of any kind.”

“He made it very clear to us that he does not lobby, but that he could direct us to the right places in Washington and elsewhere,” said Paul Branagan, who was president of Millennium Plastics when it hired Mr. Gingrich for $7,500 a month plus stock options.

As his policy interests increasingly focused on health care, Mr. Gingrich created the center, which he portrays as a think tank promoting innovative ways to improve health care delivery and save money. Companies and trade groups pay annual fees ranging from $20,000 to $200,000, with higher-paying members gaining more direct access to Mr. Gingrich.

Many of the ideas he has pushed involve the increased use of information technology, and companies specializing in that are well represented on the center’s roster. They also figured prominently in an early center initiative, teaming up in 2003 with the conservative Georgia Public Policy Foundation to promote changes in health care in Mr. Gingrich’s home state.