Flying on the wings of the wind, John Glenn, yearning for life and love and laughter, and delegates, touched down in St. Petersburg, Fla., last Sunday and tarried long enough to demonstrate some of his underestimated skills, and why he will need all of them in this marathon campaign.

In a position paper, he says that coping with the budget deficit "means controlling the rapid growth of entitlement programs with more reasonable cost-of-living adjustments (COLAs)." Appearing before the hellhounds of the press on ABC'S "This Week," he was asked what he has in mind.

Persons who think Glenn is not nimble should have seen his nifty slalom away from the question, beginning: "Well, a comment first on the overall deficit itself." And off he went with some of what Ronald Reagan will have to get used to: a Democrat taking custody of the issue of deficits.

(Columnist Mark Shields notes that Reagan was a potent "insurgent candidate" against Gov. Pat Brown, Jerry Ford and Jimmy Carter. Last Sunday, as Glenn described himself as a soldier and businessman who hates deficits almost as much as he hates war, this much seemed clear: if Glenn is nominated, another Reagan run will require a different Reagan mode.)

Glenn was speaking six days after the Reagan administration revised its budget estimates for 1984. The administration's good news was hardly news: the recovery is stronger than was originally expected. The real news was bad: the fiscal 1984 deficit projection is reduced by only $10 billion, to $180 billion. And without spending reductions and tax increases, deficits will exceed $200 billion a year through 1988 and beyond.

Glenn spoke the day before economist Alan Greenspan told the National Governors Association that federal deficits will cause a drastic slowing of the recovery in the next six months. Greenspan said that deficits cannot be significantly cut without reducing entitlement programs such as Medicare (which "ultimately will have to be means-tested").

Glenn was pressed again about a "more reasonable approach" to COLAs, and was reminded that most of the cost of COLAs is in Social Security. Moreover, when Congress recently enacted mild reforms, there were vigorous avowals that there would be no more reductions of the value of Social Security entitlements.

Glenn's answer was deft and responsible, but not without risk to him. And it pointed toward what may be a cost of the 1984 campaign. Choosing his words with care, as well he might, considering where he was (because of its retired population, St. Petersburg is, symbolically, the Social Security capital of the universe), Glenn said:

"Taking care of the COLAs (is) something that we have to do over the next several years," perhaps using a version of the Greenspan (Social Security) Commission. But "you cannot break faith with the elderly, who are beyond their working years, who cannot adjust as rapidly as people in mid-life, and so we have to be very, very careful on people who have built up this dependency on the government. And if we're going to change anything in that regard, it has to be done in the very early working years so people have a chance to adjust through their normal working lifetime."

That is a judicious, yet precise, sketch of what many--perhaps most--legislators know needs to be done: a slow, phased, delayed, moderate decrease in the value of COLAs. This is not a prescription for substantial sacrifices, but it is a departure from the pretenses that the budget can be balanced by economic growth, or elimination of "waste, fraud and abuse" in welfare or the Pentagon, or by soaking the rich, or whatever.

Even to talk about Social Security and Medicare is to walk on eggshells, and Glenn, to his credit, is doing it. But what may he and others be driven to say?

The conventional wisdom in Washington is that the need for reduction of entitlements is so widely recognized that it can be accomplished in 1985. But another 15 months of campaigning may drive the candidates to slam the door so tightly shut against reductions that no one will be able to open it in 1985. There may be a bidding war whereby they compete to see, regarding entitlement changes, who can slam the door loudest.

If such bidding begins, the nation's economic health will depend on the electorate's being discerning enough to reward those candidates--if any--who leave the door judiciously ajar.