Will it be 'Fritz' or 'Walter'?

Walter F. Mondale is now well launched. He says he is ready to be president. And from his announcement podium in Minneapolis Mr. Mondale was looking very much the president.

There was authority in his voice. He talked more slowly than usual. He seemed to be a new, very serious Mondale.

Where, one might ask, was the exuberant, sometimes playful ''Fritz'' Mondale? Where was the Mondale charm? It had to be there somewhere.

It can be argued that Mondale is a superb candidate, having had a wealth of experience in important government positions. But, it can be asked, why must such a delightful, highly personable fellow have to be ''packaged'' for television? That, clearly, is what is happening.

So at least for a while the public is going to see ''Walter'' not ''Fritz.'' And Mondale's main goal, as he walks this sober road, will be to make it clear that he is not only a well-qualified candidate but that he is also his own man.

So it is that Walter Mondale is responding to the wrong questions. These are: Can he extricate himself from having been Jimmy Carter's vice-president? Can he show that he has a set of principles and programs that are uniquely his own - and not connected to his years with Carter?

Although Mondale's advisers are telling him otherwise, he should, instead of being defensive about the vice-presidency, be proudly underscoring his performance in it. After all, he passed the chief test of vice-presidents with flying colors: No one could have been more loyal to a president than he was.

That's what vice-presidents are supposed to be. That's the prime requirement. That's what Mondale and Carter were agreeing on in Plains when Carter was selecting his running mate. They were going over their opinions on issues and, more important, their list of principles, to see if they were sufficiently in agreement to work together as a team. Further, Mr. Carter was making certain that he and Mondale would be compatible personally. And before the get-together was over, Mondale was pledging his loyalty to Carter, should the two be elected that fall.

In return for Mondale's loyalty and ties with Congress and sage advice, Carter gave a great deal. He put Mondale at his right hand - and then listened to him on issues all across the board, foreign as well as domestic. Mondale clearly became an important element in the Carter administration. And his influence never waned, despite some stories that Mondale was fading into the inevitable anonymity of vice-presidents.

Carter liked Mondale. Mondale liked Carter. It was quite a team. And Mondale, because of Carter's trust, became the most influential vice-president in history to date.

All this doesn't mean that Mondale cannot run on his own. He can and he will. But in the end he will add few if any cubits to his stature by downplaying his involvement in the Carter administration.

Mondale is being told that he can't get the nomination unless he wins the support of the liberals, and that he can't get the liberals behind him unless he separates himself from Carter. But the liberals who ask that of Mondale will be fair-weather friends at best. Where will they be if there is a final showdown between Mondale and some opponent backed by Kennedy? In such case, no matter how much space Mondale may have put between himself and Carter he will not be able to win much of the liberal vote to his side.

Mondale is indeed his own man. And those who have closely followed his brilliant political career know that he has the intelligence and experience to come up with his own ideas, his own programs. To do so, he merely has to say that new circumstances require new approaches. He doesn't have to apologize for his Carter connection.

Furthermore, who is to say that Carter will be a liability in the long run? As Mondale knows, Carter was a hard-working president who wrestled mightily, and sometimes successfully, with the enormous problems he faced. In fact, as Reagan has suffered his own defeats in dealing with the economy, there has been an upgrading of Carter in some quarters.

In the end Mondale must be himself. He will find that if he lets the humorous , often joshing Mondale surface, this will evoke the warm response he is after. He will need to get off the defensive. And he will need to embrace the Carter years - and wear that record, as much as he can, like a medal.

He will find that most people like a man - and a candidate - who does not forget his friends, even if that friend happens to be a former president who has fallen upon slightly bad days.