A close race . . .

THE 1984 presidential election could be very close. And out of this closeness could emerge positive disciplining forces in the campaign. From the vantage point of the presidential primary season - with its long stretches of ennui, punctuated by moments of turmoil and elation - it can be hard to imagine what the final campaign will look like. Opinion surveys along the way, which cannot anticipate subsequent events, can be misleading.

But experience shows that however bitter the primary campaign, party factions coalesce to some degree during and after the summer conventions, in time for the Labor Day run-up to November.

Officials in both major parties agree on this, even though it might look like wishful thinking on the part of Democrats and cautious hedging on the part of Republicans at the moment.

''We have always believed, and continue to believe, it would be a close election, whomever the Democrats nominate,'' says a Reagan-Bush campaign official. By the time the Republicans get out of their convention in August, the gap between the incumbent team and the Democratic challengers will have narrowed. It always happens. This year, whoever their nominee, Democratic elements - labor, educators, blacks, Hispanics, women's groups, peace advocates, environmentalists - will rally with enthusiasm to defeat Ronald Reagan, Republicans anticipate.

Conceivably a confluence of good economic news and international events could give the incumbent a decisive victory, but the normal two- or three-point race is expected.

Although speaking uncomfortably from the possible short side of that two- or three-point estimate, Democrats make the same case. A convention victory lends a candidate a credibility he could not have along the way. And they point out that Mr. Reagan fails to get more than 50 or 51 percent against Democrats in one-on-one match-ups.

The public, interestingly, also sees the election close in two-on-two match-ups. The latest Gallup poll gives a glimpse of what a unified post-convention Democratic ticket could do against the known GOP lineup: a Mondale-Hart ticket runs dead even with a Reagan-Bush ticket if an election were held now.

It remains to be seen whether Mondale, with secure party establishment backing, and Hart, with a stronger appeal among younger, independent voters, could find a way to embrace after last week's Texas delegate brawl. Other pairings - with a woman like Rep. Geraldine Ferraro or a Southerner like Sen. Lloyd Bentsen - could prove weaker or stronger. But the survey does at least suggest the public's ability to cut through the divisive drama of the moment and to project what a more rational alignment of political forces could offer.

In 1980, the Reagan team sought to take advantage of the natural coalescing of forces at the convention. It tried to recruit ex-President Ford - a formidable former rival - to unite the moderate and conservative wings of the party. Then it took Bush, the next-strongest rival.

For the observer: A longer view of the 1984 race may be the more useful to hold. The potential closeness of the outcome could mean a healthy competition for every faction's attention. It also offers pressure on both sides to search out common ground - as is already evident in Washington's current budget deficit struggle, and in dealing with Central America.

For the participants: An expected close race should argue for more disciplined, not more desperate, campaigning, and for more responsible debate.