BY EVERY RECKONING, Fritz Mondale is the front-runner for the Democratic presidential nomination in 1984. That's good, right?

Wrong, according to a lot of pundits. To hear them tell it, being the front-runner is more of a danger than an asset; it puts Mondale at a disadvantage to those who trail him. What's going on here anyway?

History, for one thing. Those who view Mondale's prospects through the glass darkly are remembering the political failures and disappointments of the past 15 years. The memory, particularly, of George Romney, Edmund Muskie and Edward M. Kennedy, all of whom showed strong early foot out of the gate only to stumble at the first turn -- on the way to Iowa and New Hampshire -- remains remarkably strong.

The experiences of the aforementioned gentlemen seem to feed the theory that being the front-runner inevitably subjects a candidate to intense public scrutiny, which is bound to be bad for him. This is an interesting concept.

You might think, in a culture that prizes success and victory above all, that being the front-runner would confer certain advantages in terms of raising money, getting press attention, recruiting staff and attracting support. In fact, it does.

Attributing the failures of Romney, Muskie and Kennedy to their fast starts is simply bad history. They came to grief for good reasons that had little to do with their early showings in the opinion polls and with the press.

Kennedy's 1980 campaign didn't fail because he led Jimmy Carter in the polls all through 1979. It was obvious in the now-famous television interview with Roger Mudd that Kennedy had a serious problem when he was asked why he wanted to be president and came up hurting for an answer.

Ask anybody on the street what they would do if by some miracle they found themselves in the White House and nine out of 10 would have something in mind, if only a desire to order the IRS to audit the cretin next door who runs his lawnmower at 7 a.m. on Sundays.

Kennedy contended that the question caught him by surprise. This in turn caught everyone else by surprise, since he had been intimately involved in presidential politics for 20 years and had been a U.S. Senator for nearly that long.

Then Kennedy proved to be a remarkably inexperienced and maladroit campaigner -- at first. He learned fast but by the time he got his act together, both programatically and as a campaigner, it was far too late.

Muskie -- though an excellent senator and public servant -- may have been temperamentally as unsuited a presidential candidate as we have seen in our time. His hair-trigger temper could blow up tempests out of a seemingly clear sky. That famous temper recedes just as suddenly, leaving Muskie serene and apparently oblivious that anything happened, while everyone around him looks as though they had just gone through a typhoon in a rowboat.

And any man running for national office in 1968 and 1972, as Muskie did, who could take questions on what he would do about the Vietnam war as a slur on his personal integrity, as Muskie did, obviously had a political problem totally unrelated to his standing in the polls.

At this time in 1967, Romney led Richard Nixon by 45 percent to 41 percent in a Gallup Poll of Republicans' presidential candidate preference. A year later he had no real support at all.

Romney appeared to be as divided in his own mind about the Vietnam war as the nation was. It was apparent that he had little enthusiasm for the war, but he knew he had to show some if he wanted to win the GOP nomination in 1968.

This was a dilemma shared by many at the time, but Romney compounded it by conducting his internal debate in public. So, when he made his unfortunate remark that he had been "brainwashed" by U.S. officials in Vietnam -- and he was by no means the only victim -- his remark ignited a political explosion that blew him out of the presidential waters.

Every election cycle has its own political dilemma. The Democrats' problem now is to overcome the popular belief that they are the "more-of-the-same" party that is counting on winning by default when the Reagan administration crumbles. The Democrats have to come up with plausible-sounding approaches to the economy, national defense and the role of the federal government in the 1980s. When Ronald Reagan succeeded at that, he was swept into the White House.

A major peril for front-runner Mondale is the temptation to play the coalition politics of the past by catering slavishly to the traditional groups of the Democratic coalition -- labor, minorities, liberals, civil libertarians, nuclear freeze advocates and the constituencies of a host of federal social and welfare programs, plus such newcomers as the Gay-Lesbian Coalition.

Mondale has already made a couple of twitches in that direction, and the old constituent groups will be pressuring him constantly to make a lot more. If he doesn't strike the right balance, he could end up as the nominee, like, say, George McGovern, but turn out to be unelectable.

But Mondale and his advisers are aware of this. "He has to keep focused on the fact that this is a substantive race and that he has to have programs and solutions to the long- term problems," says Jim Johnson, Mondale's chief strategist. "We have to strike a balance between the primary and general campaigns, seek the endorsement of labor and other party elements but remain independent."

If Mondale can fill Johnson's prescription while enunciating an approach to the country's problems that convinces voters that he knows where he wants to take the country, his front runner status today will easily be converted to the Democratic nomination in 1984. He'll remind us that there's nothing wrong in starting the race outtin front, provided you know how to stay there.

By the way, at about this point four years ago, the polls showed that there was a clear front-runner for the Republican nomination for president. His name was Ronald Reagan.