White House media adviser Gerald Rafshoon has sold Rafshoon Advertising Inc., the Atlanta agency that helped make Jimmy Carter president in 1976.

William Stack Jr., the trustee for Rafshoon's business holdings, sold the firm April 20 to Howard Rothchild, the current president of the agency, and a second investor whom neither Stack nor Rothchild would identify. The parties to the transaction also declined to disclose the price paid for the 16-year-old firm.

Rafshoon still owns his Washington-based public relation firm, Rafshoon Communications, though his interest is managed by his trustee.

Rafshoon, who left his agency to join the White House staff last July, said yesterday he sold the firm because he is not in a position to "take care of it" anymore. He said the sale was not related to publicity over the past few months concerning the agency's financial arrangements with Carter's 1976 presidential campaign.

The campaign, which was strapped for cash through most of the early primary races, counted onb a continual extension of credit from the Rafshoon agency to conduct its media effort.

At its peak, the Carter primary campaign had $645,000 in debts and obligations to the Rafshoon agency, according to the campaign's finance reports.

Questions have been raised in the press as to how the agency-without outside assistance-was able to extend the credit to the campaign. Outside assistance could be considered an unreported loan or contribution to the Carter campaign.

In addition, there have been questions about whether the extension of credit from the agency might have constituted an illegal corporate loan. According to Federal Election Commission regulation, and extension of credit to a campaign by a firm would be improper if it were not a normal business practice for the company.

The firm ahs repeatedly stated that nothing improper took place. "No credit was extended to the campaign from bank loans or any other sources outside the agency's operation," Stack said.

The firm did receive a loan and line of credit fdrom Bert Lance's National Bank of Georgia in 1976. The money was used to pay agency suppliers after the bankruptcy of several clients, Stack told a reporter.

Stack also declared that the credit extended to the campaign was "a legal, normal and proper" business transaction that did not violate federal campaign law.

Records regarding the National Bank of Georgia 's relationship with the Rafshoon agency were subpoenaed last September by a federal grand jury investigating Lance's banking practices. CAPTION: Picture, GERALD RAFSHOON . . . left agency last July