Watching the Democratic Party and Teddy Kennedy together in Philadelphia, you might be reminded of an Irish courtship.

What's Irish about it is that it is a romance that seems to have no resolution. Everything has changed, of course, but still in the Celtic version of what is now called "a meaningful relationship," feelings are often put aside for other considerations. One or the other is waiting for an aged parent to die, for a younger brother to get a job, an older sister to find a husband. There's always a snag, and the years go by.

Ever since 1968, the Democratic Party has been sighing that it wants another Kennedy in the White House. Teddy, for his part, has intermittently indicated his willingness to accept the family destiny. But here we are in 1982, and who is to say how much further along things really are?

Teddy's elegant, rousing speech caused by far the biggest commotion of the mid-term conference. A similar effort in Memphis in 1979 and a post-defeat tour de force in New York in 1980 had the same effect on Democrats, suggesting that before or after they vote, Democrats have eyes for nobody but Teddy.

His commanding presence, his big, rallying voice had them standing on their chairs, waiting to cheer. He has shed seven of the 20 pounds that Richard Nixon says he must lose if he is to be the nominee. His jawline has re-emerged from his massive face. He appeared confident and relaxed.

The speech had everything: an opportunity for audience participation when he asked, "Are you better off than you were two years ago?" and the occasion for a creditable imitation of FDR saying how much Republicans care about Social Security. And there was a final trumpet flourish of Tennyson.

Who could ask for more? Many in the hall did not. They thought they had heard the acceptance speech of the Democratic nominee in 1984.

But the snag is still there.

What the followers of his only rival, Fritz Mondale, euphemistically call Kennedy's "personal difficulties" remain. The Democrats know they can nominate him; the Republicans already have. But they are not sure they can elect him.

Three years ago this summer, Kennedy was surging in the polls, swamping incumbent Jimmy Carter. Fellow Democrats were importuning him, secretly, to save the party. Chappaquiddick, the polls and the pols said, was forgotten.

But the campaign on which he finally embarked was a prolonged embarrassment. Kennedy was subjected to humiliations and snubs that would have crushed a candidate for city council. But once they had safely rejected him, the Democrats at their New York convention tumultuously reaffirmed their passion for Ted Kennedy.

House Speaker Tip O'Neill scurried to his seat in Philadelphia's Civic Center for the final moments of the ovation for Kennedy. After it, he said, "If the economy is bad, Teddy is a cinch. If it's not, he's got a lot of problems."

The Rev. Robert F. Drinan, chairman of Americans for Democratic Action, said, "Everywhere I go, people say 'I love Teddy on the issues--but . . . . ' And they don't need to finish the sentence."

A woman in the Massachusetts delegation, frantically shaking her "Kennedy nuclear freeze" poster, gasped, "Oh, yes, I guess Chappaquiddick is still in people's minds, but it's watered down now."

One passage in Kennedy's speech seemed autobiographical: " . . . We have had our scars and our sorrows, our failures and our fears. We have made our share of mistakes, and we have felt the sting of defeat. But we have stood our ground, and the struggle has made us stronger."

Kennedy loyalists echo that. They say that the country has forgiven Teddy his trespasses because he bore his defeats with gallantry and grace.

"It was the hostages that did it," they protest.

The question is whether, if he runs, he will be running against himself again or against his only rival, Mondale, who had only to survive Philadelphia. His speech, according to the experts, "took him off the life-support system."

Mondale's personal luggage--he carries no rumors or reputation--is lighter than what Kennedy carries. But he has what some contend is a matching negative, his Carter connection. Jimmy Carter stirs ferocious antipathy among Democrats. His name was the big unmentionable in Philadelphia. Mondale surreptitiously sandwiched it in between Kennedy and Cranston.

Carter makes Mondalians flinch when he makes references to Mondale as his most intimate adviser. Recently, Carter said Mondale was involved in every major decision of his administration.

Mondale's people say that by 1984, people won't be saying 'Don't forget the $50 rebate; don't forget Billy Carter.' " The underlying assumption is that Teddy Kennedy's "personal difficulties" will prove to be the enduring liability.

In the end, they think, Democrats will settle down with Mondale, who is almost as liberal as Teddy Kennedy, if not half as exciting.