From the start, the name of the game was to get Rep. James J. Florio (D-N.J.) to do as the jingle advises and "remember the soup."

It was industry lobbying at its most sophisticated: Low key, light-handed, lightning quick, behind the scenes, constituent-based and targeted at a single swing legislator who held a key vote on a tough consumer issue.

And in the end, it all came together. On the eve of a scheduled subcommittee vote last month, Florio bowed to the wishes of the food industry interests in his district, led by Campbell's Soup Co., and withdrew his proxy in support of a measure to require that foods be labeled for sodium content.

Because he would have been the 10th "yes" vote on the 20-member House subcommittee on health and the environment, his move effectively killed the bill.

The sudden turnaround came as a bitter disappointment to consumer and public health activists, who had viewed Florio as one of their most reliable allies in Congress. They are trying now to return him to the fold with a belated letter-writing campaign.

The issue is a hot one. Salt is America's new food villain, and public health activists find they are in a rare posture for the anti-regulatory 1980s: on the offensive. "This bill is the only shining light this year on the Hill for consumers," says Ellen Haas, consumer director of the Community Nutrition Institute.

Their drive is fueled by a large body of fresh medical evidence linking salt intake to high blood pressure, and, indirectly, to strokes and heart attacks, which together account for half of all deaths in this country.

Doctors, whose professional associations have swallowed their unease with regulation long enough to urge adoption of the bill, say that 60 million Americans with diagnosed or borderline high blood pressure should be on low-sodium diets. The average American consumes 20 to 50 times more sodium each day than his or her body needs.

The food industry does not dispute these findings, nor does it take issue with the desirability of sodium labeling to permit high blood pressure-prone consumers to make informed choices at the grocery store. Where it draws the line is at regulation.

"The issue is whether the government has faith in the industry," says James May, vice president of the Grocery Manufacturers Association, which argues that competitive market forces will induce the industry, without the guiding hand of big brother, to label for sodium.

He cites Campbell's as a case in point. It produces a line of products high in sodium content. A single serving of Campbell's tomato soup, for example, contains 932 milligrams of sodium, or nearly five times the average adult daily requirement.

In response to growing consumer concerns, Campbell's has begun to sell a line of low-sodium soups, and to label all of its regular soups and broths for sodium content. It is considered a leader in the field among the major companies and is proud of its efforts.

"I've got a father with high blood pressure, and I myself don't salt my food," says Bertram Willis, director of government relations for Campbell's. "We don't want to leave the consumer in the dark about sodium content."

Campbell's also does not want the government to come in and dictate the print size and type face of its labels.

That is the case it made to Florio, as forthrightly and responsibly as possible. The word "pressure" is often associated with industry lobbying; in this instance, the sell was strictly soft, and the product goodwill.

When, for example, the top executives of the company had Florio over for a private lunch around the first of the year, the labeling issue was not the major point of discussion. Rather, the conversation centered on the revitalization of Camden, a city in which Florio is the dominant political force, and Campbell's, with its 2,800 workers, a major employer.

All that hinted of lobbying that day was the menu. The meal began with Campbell's new low-sodium tomato soup, which had the desired effect of turning the conversation to the labeling issue. Florio said at the time he was undecided. The executives didn't push.

"At no time did we make this a vigorous lobbying effort," said Willis. "I can't remember sending a single letter on it, and we certainly didn't march a delegation of vice presidents down to Washington."

Like any good salesman, Willis knows his market. "Nobody heavy lobbies me," says Florio, an independent-minded ex-amateur boxer. His response is similarly terse to a charge leveled by consumer groups that he kowtowed to industry beause he is considering a Senate race this year that would carry a $2 million price tag: "I don't even respond to things like that," the congressman said.

After the luncheon, Willis made a point of bringing up the labeling issue whenever he touched base with Florio during his regular lobbying trips to Washington. The congressman told him that, despite his past active support, he had become "disenchanted" with labeling. "Nobody reads them," he now says of the saccharin labels he helped to legislate.

Willis sensed a potential convert, and so did May at the Grocery Manufacturers Association. Still, within congressional committees, the ties of loyalty are strong, and when two longtime pro-consumer allies, Rep. Albert Gore Jr. (D-Tenn.) and subcommittee Chairman Henry A. Waxman (D-Calif.), urged Florio in early February to give his proxy in support of the bill, he went along.

Florio insists he had misgivings from the start; Gore verifies that account. But Gore says steps were taken to mollify his concerns. As a concession to industry, for example, an amendment was drafted that placed the labeling requirements on a voluntary basis for 18 months. If, at the end of that period, at least 75 percent of the industry was in compliance, the requirements would remain voluntary.

Industry didn't think that went far enough, and on Feb. 22, the day before the scheduled vote, May gathered a group of food producers from South Jersey to meet with Florio for breakfast at the Mount Laurel, N.J., Hilton.

Forty industry representatives responded to May's mailgram, ranging from the giants like Campbell's to the mom-and-pop operators like Jim Sclafani, a food packager from South Jersey.

Florio presided and invited comment. Willis argued that the 18-month trigger period really wasn't voluntary at all, because an individual company had no way to control whether it would become mandatory.

Sclafani took a more impassioned tack. "There are two things in life I fear," he reportedly told the congressman, "God and the Food and Drug Administration." The FDA would administer mandatory labeling regulations.

Florio listened to all viewpoints (consumer and health groups were not invited). He gave no commitments. Then he returned to Washington and instructed his staff to withdraw his proxy.

Lacking a majority, the labeling sponsors pulled the bill from the subcommittee calendar. The vote was never held.

Consumer groups, who never got wind of the industry effort until it was over, are now busy trying to play catch-up with Florio. The congressman, meanwhile, says he is looking for a middle ground.