Have national political conventions finally outlived their usefulness?

Plenty of Americans must be wondering about the need for this institution and what its future should be now that the Democratic national convention in Atlanta is coming to a close.As is well known, the Atlanta convention settled little that wasn't decided by the presidential primary elections even before they ended six weeks ago. As expected, the long struggle for the party's nomination concluded in a display of unity between Michael Dukakis and Jesse Jackson, since both men and the party itself would have suffered without it.

Though the party's new platform represents some concessions to Jackson and the party's liberal wing, it is still a relatively moderate document - again, as expected. After all, the Democrats would have to be remarkably obtuse not to have learned from its painful experience four years ago when Walter Mondale was buried by his call for higher taxes.

Even the Democrats' overall swing toward the middle of the political spectrum and away from the party's previous embrace of narrow-interest or special-interest groups had been engineered well in advance of the Atlanta convention.

For that matter, when the Republicans meet next month in New Orleans, their national convention will be just about as cut-and-dried as the Democrats'.

So what's the point, if any, in holding these quadrennial exercises, aside from giving delegates a chance to cheer and demonstrate on cue and listen to a few speeches?

Well, as a matter of fact, the political conventions really do serve some useful purposes - though not as many as they did before the proliferation of presidential primaries.

For one thing, the conventions can revive public interest in an important process. After a long series of primary elections and several weeks without suspense about the nominations, public attention to the presidential election understandably flags. This year, audiences for network TV election coverage began to decline by Super Tuesday, which led the evening news shows to cut the air time devoted to the remaining primaries.

Conventions - with their ceremony and at least a flavor of drama - remind the public that something significant is going on. "They provide," as Political Science Prof. Paul Quirk of the University of Illinois puts it, "the sense of a formal beginning to the general election campaign, a point at which to take notice."

The national conventions also can capture large audiences for some important speeches. The most important are the nominees' acceptance speeches - the longest and possibly the most revealing speeches they ever give to the entire country before the election. Other convention speeches also can bring new leaders to national attention.

Consequently, watching the conventions and reading about them can help voters make up their minds about which party they feel most comfortable with.

Even so, the fact remains that the national political conventions are becoming less significant, while the presidential primary elections are becoming not only more important but also more time-consuming, fatiguing, and expensive.

Long after both the Democratic and Republican conventions are over and the next occupant of the White House has been decided, America really ought to reassess and try to improve the way it picks its presidents.