EUGENE McCARTHY'S approach to Presidential politics was startling in conception, magical in impact, darkly unpredictable in outcome. In person and on television, McCarthy's square features, rugged voice and slightly receding hairline spelled nothing so well as "President." And while the country hasn't actually had this image in the White House since Franklin Roosevelt, Americans still know it when they see it. It gives them pause, which in McCarthy's case was half the battle: once listened to, his message came across with unmistakable intelligence, groping caution and unimpeachable patriotism.

Over the weekend, Americans were treated to a radically different political style in the person of Robert Kennedy. Whether by design or not, Kennedy suggests youth as opposed to wisdom, bashfulness as opposed to frankness. He worries a lot about his hair and counts his teeth as a clear asset. Like his older brother, he is attracted to a vague kind of fancy rhetoric, consisting chiefly of parallelisms (often redundant) and alliteration (often meaningless). This means he is attracted to a speechwriter named Ted Sorensen, who apparently drafted Kennedy's kick-off speech Saturday and who cab boast some of the decade's most quoted catch-phrases, including the sinister but obviously popular "Ask not what your country can do for you" line. Kennedy's delivery is fast and clumsy, and his voice squeaks along sometimes unaffected by dropped sentences, grammatical non-sequiturs and patent evasions.

KENNEDY is said to be consummate behind-the-scenes man, a reputation deriving largely from his masterful work for brother John in 1960. Public opinion polls of the last year and a half suggest he is also a popular as any politician has a right to be. So it shouldn't be any great leap of the imagination to view him as virtually the ideal candidate, a one-man combine of the goods and the ability to sell them.

McCarthy probably never had even a fighting chance for his party's nomination. What he did have was a chance to be an agent--alongside catastrophe in Vietnam, or chaos in the United States, or both--of an open Democratic convention in August. A Dien Bien Phu, even in miniature, coupled with race riots on a scale approaching open revolt, could make Johnson so clearly unelectable as to be unnominatable. It was this picture, or one quite like it, which drew Kennedy into the race.

But Kennedy's candidacy offers little more prospect than McCarthy's of dumping President Johnson--for two reasons. First, like McCarthy, Kennedy is at the mercy of a world and national scene over which he has no influence. Catastrophe of a grandeur sufficient to demolish LBJ, should it occur, might demolish him under any circumstances, with or without previous opposition in the primaries. Second, Kennedy by virtue of his name and reputation must rack up overwhelming margins to equal the impact of McCarthy's 42 per cent in New Hampshire: if the Kennedy charisma proves less dynamic in the event than in the propaganda, Kennedy will be committing premature political suicide.

For all the risks, Kennedy's decision makes sense in purely personal terms. His chances in '68 may be dim, but what with the strong possibility of a Republican President next year, '72 looks even dimmer. The man who beats Johnson--call him President Nixon--would likely remain in office for eight years, sustained by a period of post-war reaction and by the dictates of political fashion. By '76 Kennedy could be nearly as anachronistic as Harold Stassen in the current campaign.

FOR Kennedy, then, '68 is the lesser of at least two evils. It is also a confession of deep political unwellbeing. Even as he announced his candidacy, the junior Senator from New York looked less like a future President than ever before. He has set a nearly impossible goal for himself in trying to unseat an incumbent President, but the realization of that goal will not assure Kennedy of the nomination. As long as President Johnson remains a major influence, he will be in a good position to veto a least one candidate, and he will surely use his veto on his old friend Robert Kennedy, even if the alternative should be a member of the same family.

The test of RFK's electoral strength will be California. If he ekes out the necessary plurality over Johnson and McCarthy, he will at least still be in the running, which is to say able to reap the reward if the President falters. If, on the other hand, Kennedy achieves no better than 35 per cent, as against, say, 40 per cent for LBJ and 25 per cent for McCarthy, he will have died a quiet death and be remembered, if at all, as "that other Kennedy."

One hesitates to label such an unpromising campaign "opportunistic." Kennedy is, after all, risking everything in a year when he might risk next to nothing. He has thrown in with the Democratic Party's bastard wing, not even sure they will accept him. If he has miscalculated, it is not so much out of opportunism as out of conviction: the conviction that Robert Kennedy has what it takes in this banner year of American political history. Given the alternatives, Kennedy's conviction is a tempting one.