Like Wyndham Lewis, who called himself "a lion in an ill-run zoo," Edward Kennedy, early in his candidacy, found himself promenent but caged. Some of the constraints -- his taking on an incumbent, his personal troubles -- tied him down then, and tie him down now. But regardless of how he fares in the Super Tuesday primaries of June 3, Kennedy has not let the ill-run zoo of the primary process either demoralize him or dilute the ideals of his progressive politics.

Kennedy's liberalism was an early catch-pan for speculation. It was said that, being a practical politician, he would go with the prevailing winds and move rightward toward the center. That, supposedly, was where the country was. Watching Teddy become an ex-liberal and suddenly going blurry on his once-sharp convictions promised to be still another proof that the left was as lifeless as a window mannequin.

Whatever the temptations -- and the temporary hiring of Herbert Schmertz, Mobil Oil's man for public-realtions slick, ominously suggested that a new image for the candidate was about to be fashioned -- Kennedy didn't bend.

It is true that for a brief period after his announcement the only identify he was Kennedy, a Kennedy -- not Kennedy the liberal. His high standing in the pre-campaign polls lulled him into thinking that not only was he immensely popular but that the public knew his positions on the issues, which it didn't. With every friend and flunky telling him that "the presidency is yours for the taking," he neglected to do what John Kennedy did in preparation for his race in 1960: organize madly.

Once into the campaign and seeing that he needed to gather his wits, he stood firm with the progressive liberalism that was both the poltiical philosophy of his brother Robert and at the core of his own service in the Senate.

In one recent primary, Kennedy called on George McGovern for a televised endorsement. Cynics dismissed this as the ultimate sign of desperation. But it revealed that Kennedy was large-minded enough to understand that he had an alliance with American liberalism and that he was at the service of that alliance, not the other way around. Why shouldn't the embrace of George McGovern be welcomed? He was, and remains, a major voice for humane politics and a reliable deliverer of progressive thinking.

That Kennedy has resolutely stayed on the left has been a strong defense against the charges about his character. Was 17 years of holding hearings in the Senate to give forums to refugees, farmworkers, Head Start mothers, teen-age parents, unorganized laborers, Indians, Mexican-Americans, the unemployed and others on the system's periphery no more than some packaging for a power-driven careerist?

If it was, the ribbons on the package would have come loose during the primaries. The daily tensions and trials of underdog campaigning would have been to harsh a torture for someone whose convictions weren't shaped by goals larger than his vanity. Had he lacked character, Kennedy would have walked away from those he once championed, declaring, in a line from Jimmy Carter, that their problems had become "manageable" and he must now go on to other urgencies.

Once the integrity of Kennedy's liberalism was established and he came forward with a program of substance that offered some promise for the 1980s, he had the problem of getting across how successful his challenge actually was. No elected president has suffered as many primary defeats as Carter and continued on anyway. For Lyndon Johnson, even a near-loss in New Hampshire in 1968 was enough to wake him up to his unpopularity and force him out. In 1952, Estes Kefauver beat Harry Turman in New Hampshire. That led to Truman's not seeking another term. Carter -- though beaten by a challenger in New York, Connecticut, Massachusetts, Michigan, Pennsylvania, District of Columbia, Alaska -- stays on. He isn't the picture of a president in command of his party.

Whether he wins or loses next Tuesday, Kennedy has pulled off one amazing achievement. He is a liberal who has not disenchanted other liberals.

If it happens that Kennedy has won fewer new friends than expected, the more impressive fact may be that he didn't drive away his old friends. He led them, as they asked him to do.