MIAMI--The endless presidential campaign of Walter F. Mondale, begun in 1972, suspended in 1974, resumed with the vice presidency in 1976 and continued almost uninterrupted since then, has for the moment come to a halt. His flight to Washington has been canceled.

And so the man who was once vice president of the United States and who would like to be president of the United States is nose to nose with airline employes, being told one minute that there were not enough passengers to make the flight worthwhile ("insufficient participation") and the next that there was equipment trouble. Running for president, like life itself, is an educational experience.

So Mondale and two aides head for a nearby lounge to await yet another plane. The former vice president gets recognized. A man wishes him well; so does a woman. Some people say hello, most do not and one kid, fresh, clean and almost radiant, calls Mondale over. The former vice president approaches with his hand out, but withdraws the offer when the kid tries to convert him to some religion or another.

The campaign, of course, has begun. Former Florida governor Reubin Askew is already on the road. So, to an extent, are Sens. Gary Hart, Alan Cranston, John Glenn and of course Edward Kennedy. The Democratic Party senses victory, first in the 1982 congressional elections and then in 1984. The conventional wisdom today is that Ronald Reagan's presidency is a failure and the man himself, like the man who preceded him, will be a one-term president.

This is what Mondale thinks and this, he says, is what the people are now telling him. The Reagan program is now talked about in the past tense.

Even businessmen have written it off and so total and stark has been the Reagan collapse that the man who was Jimmy Carter's vice president no longer has to answer for the mistakes of that administration. The agenda now is the perceived mistakes of the present administration. Jimmy Carter, not even two years out of office, has become the president who never happened.

Maybe there is another way to run for president, but no one is quite sure what it is. New Hampshire and Iowa, the first primary and caucus states, seem to reward the candidate who courts them the most. Put time in and you'll get votes out. The same holds for the other primary states.

The country remains as vast as ever--a collection of provinces. When running for president, it pays to be provincial.

In Miami, for instance, Mondale is asked about refugee problems. It is the sort of issue that brings people to blows, that has split this community every which way, that is both a national issue about immigration policy and also a neighborhood issue. After all, we are talking about the people moving in down the block.

So Mondale walks this one very gingerly. Mostly he answers by not answering, by acknowledging the complexity of the issue and how it is local, but knowing also that he will have to do better. This is what the early outings are about: doing better. All candidates need to sharpen their timing, get their answers down, learn the applause lines. In Florida, spring training is not just limited to ball players.

But mostly for Mondale the issues are the standard ones of the Democratic Party: equity, social justice. Liberalism, updated and pragmatic, to be sure, is no longer the butt of every political joke. It is somewhat fashionable again because Ronald Reagan has dragged it back into the mainstream. Mondale cannot thank the president enough.

He calls Reagan a "radical," a term he uses over and over again with obvious relish. It's way off the mark, though. If Ronald Reagan is anything, he is a reactionary.

That the two are different is something that seems to have escaped not only Mondale, but most of the Democratic Party. After all, what might be needed is precisely some radicalism--an attempt to really deal with an economy that has been ailing a long time. No matter. The presidential campaign proceeds. It's business as usual. The candidates are out in the field, building local organizations, assimilating a billion local issues, shaking a trillion hands, getting close to the people and, of course, wasting time in airport lounges. It does not matter anymore what time it is in America. It is always campaign time.