At a cocktail party the other night, two people were talking about Jimmy Carter. "Did you see the cartoon of him sitting in the huge chair looking like a tiny ant?", the man said to the women. Laughter. Then: "Did you see the one . . . "

What Europeans have been seeing of the American president lately, and what they have been saying, is hardly flattering. Newspaper front-pages carried that disturbing photograph showing Carter straining and staggering during his recent run in the Catoctins. One page-one headline, with literal accuracy but also with devastating political symbolism, recorded that news this way: "A Pale, Wobbling Carter Quits 6-Mile Foot Race"

And that, as much as anything, sums up what appears to be a uniformly negative view of the American president.

Now pictures of Sen. Edward M. Kennedy peer from every newsstand, and people seem to take for granted that the last of the Kennedy brothers will lead America into the 1980s just as John Kennedy's presidency ushered in the 1960s. Already a draft-Kennedy group -- the Democratic Committee Abroad for Kennedy for President -- has been formed by U.S. citizens living in Europe. It's headed, ironically, by two Americans who managed the Carter campaign among U.S. voters in France in 1976. One of them was quoted in Paris this week as saying their allegiance has shifted because Carter "has disappointed his supporters in carrying out his White House job." Which fits exactly with the words being uttered both in the United States and abroad. LEADERSHIP

Aside from the name, Kennedy remains rather enigmatic here, with people expressing uncertainty about what his presidency would mean. "After all," said an Italian politician with a shrug, "what does the New Frontier mean today?"

But there seems no doubt about the judgment on Carter. He's regarded as the weakest president in memory, and you don't hear the kind of personal sympathy for his problems that are expressed in America. Depending on the point of view, Carter is in difficulty either because he seems from this vantage point to receive conflicting advice or because he appears confused about what direction to take. Even when people agree with what they perceive as his policy -- a more flexible approach to the Palestinians, for instance -- they see him as too weak politically to implement it.

More often than not, they are critical of the president's general leadership. Carter has come under much criticism here over the Soviet-brigade-in-Cuba issue. "Not because the Russians have troops there," an English political observer remarked, "but because Carter clearly didn't know how to handle the issue."

The real problem, of course, goes far beyond the fragility of Carter's grip on the American political system. It concerns the view of American leadership in the world and the common problem facing all Western nations. As a writer here said, it's one thing to live amid the folds and creases and instability of Italian political life. But the idea of an America unable to govern itself -- an idea that appears to be taking hold -- becomes deeply disturbing.

A Communist Party official said essentially the same thing in different words: "America seems to be facing a crisis of goals," he said, "and in that sense, America is a mirror of the more general crisis in the West. It is no longer clear what kind of society America wants to create or fight for, and when there is that kind of instability in a country like America, there is instability in the world."

The Italian government is proposing a new austerity program calling for periodic blackouts, raising the cost of electricity by 15 percent for both industry and home consumers, and banning central heating elsewhere between the hours of 11 p.m. and 5 a.m. All this is supposed to help combat the raging inflation rate, presently running at 16 percent annually here, but no one really expects the new program to work.

Just the other day, the government raised the price of gasoline for the second time in less than two months, boosting it close to the $3-a-gallon mark. Now if you think this will stem the Italians' love for and dependence on their cars, any more than U.S. attempts to cut back gasoline consumption have worked, you surely don't know Italy.

There was a general bus strike here recently, and everyone in Rome must have brought out his or her car. The result was what may have been one of history's grandest traffic jams. The sight of these cars, snarled, stalled and intertwined, and the smell of those gasoline fumes rising in the air was memorable.

"No one's willing to sacrifice," the Italian senator says, and any talk of austerity is considered repressive, negative. You can't convince people to do without, unless you offer them some positive reasons why a different lifestyle may prove beneficial to them. There has to be a spirit of idealism. They will not accept austerity as punishment."

Translated, all this comes down to the same kinds of hunger for different leadership that affects an America wrestling with similar questions. With unintentional irony, it was a Communist politician who offered the gratuitous but not bad advice on how the U.S. can solve its problems, and thereby help the world. "What America needs is a Roosevelt of the 1980s," he said, "because now everything has to be reinvented."

Fine enough, except he didn't say where to find one.