Gannett Co., with more than 80 daily newspapers the nation's largest press chain, began distributing yesterday prototype editions of a proposed national daily called USA Today.

Two separate versions of a four-section publication, each with 40 pages but featuring somewhat different contents, design and graphics, were handed out to advertising and media executives in advance of extensive opinion sampling throughout the country on reaction to the newspaper.

USA Today, said Gannett Chairman Allen Neuharth in a note of to readers on the front page, "proposes to be national in scope, in both news and advertising, and different from any publication now available."

The overall contents of the prototype edition, however, appeared to be a mix of standard features in a variety of publications. The main news section includes brief stories from every state in the union as well as the District, where a Gannett-based subsidiary has been developing plans for the proposed publication.

There are separate feature and sports sections, with detailed entertainment guides and full reports on major and minor league sports. One prototype edition has a separate financial news section with some stock market tables. The second prototype edition places business news at the back of a second feature section and has no stock tables.

In the prototype editions, there is a heavy emphasis in news columns on crime and sex. In the state-by-state roundup, the lead item from Delaware concerns a raid on pornographic entertainment centers; one of three Maryland briefs deals with sentencing of a state official on sex changes and the Virginia section of two items starts out with the sentencing of a Martinsville man in a murder case.The second Virginia item is about an oil spill in Fairfax.

The feature, sports and financial reporting appear to be more conventional, however -- apparently part of the mix that Gannett officials expect would be attractive to people who travel about the country much of the time. This group has been pinpointed as a primary market.

Maurice Hickey, president of Washington-based Gannett Satellite Information Network and a chief planner for the newspaper, said recently that 28 million Americans (750,000 persons every day) traveled on scheduled airlines in 1979. An average of 1.5 million persons stay in hotels and motels each night, he added.

"Our goal is to reach the mobile, active, upscale market," he told a newspaper forum convened last month by newspaper analyst John Morton of John Muir & Co. last month. "We wouldn't expect to be the first [newspaper] buy every single day, but we hope to be the most attractive and familiar alternative to hometown newspapers -- especially for those people on the go -- and people who have moved to new homes in recent years and retain strong interest in areas where they formerly lived," Hickey explained.

Analyst Morton, after looking at his copy of the prototype edition yesterday, said he would be surprised if Gannett does not go ahead and begin publishing the newspaper.

To date, Neuharth and other Gannett officials have declined to say how much money they might invest in the publication. They have hired two opinion sampling firms to monitor reaction to the prototypes and promised a decision on whether to go ahead late this summer or early in the fall.