The drafters of the 1984 Republican platform presented their handiwork in Dallas with the announcement that "on the 20th anniversary of Barry Goldwater's historic campaign to restore America's greatness, we hold up our 1984 platform as evidence that in the end he and his cause were victorious."

It took a while for Goldwater and his Sun Belt conservative followers, who wrested control of the GOP from the eastern liberal establishment 20 years ago, to realize that they had in fact won, but the conservative 1984 platform and convention are all the proof of that victory that anyone could need.

Many more such victories, however -- the conservatives dominant in Dallas, with the ubiquitous presence of evangelical Christians and the harsh, partisan rhetoric reminiscent of the GOP convention in San Francisco 20 years ago -- and the Republican Party will be undone, at least in realizing its hope of once again becoming the majority party.

This hope on the part of the GOP is a reasonable one because of one simple demographic fact: eligible voters age 45 or younger outnumber those over 45 by about 93 million to 70 million, and more young eligible voters enter the electorate each year. The political system is in transition, and the party that wins the allegiance of a majority of this group can reasonably expect to be the majority party into the 21st century.

To a great extent those in this population bulge -- the so-called World War II and post- World War II "baby boom" generation -- are targets of opportunity for both parties.

Their political identities, unlike those of their elders, are not defined by the New Deal -- by being either for it or against it. Unlike their elders, many neither want nor expect much from their government except to be left alone.

To many under 45, the federal government is not the benign social referee of the welfare state. They are more likely to equate it with the Vietnam War than Social Security or unemployment compensation.

The polls indicate that this group tends to be more fiscally conservative and anti-big government and big labor than many of its elders, so the economic planks in the platform may suit many of its members just fine. The polls also indicate that Ronald Reagan is popular with younger voters, to a great extent because of his personality and perceived leadership qualities.

These younger voters also tend to be more liberal -- "almost libertarian" in the words of Robert Teeter, one of the GOP's leading pollsters -- on social and cultural issues such as choices of life style, sex, drugs. They are less impressed by the "traditional values" of family, religion and patriotism so assiduously celebrated at both conventions this summer, particularly the Republicans', and this puts them in conflict with their elders and the social planks in the GOP platform.

A lot of people contend that platforms aren't worth the paper they're printed on, that they're two-day stories of interest only to their drafters, which in both parties are the activist, ideological wings.

But platforms are a useful look at where the controlling element of the party is at a given time. The rest of the Republican Party, including its candidates in 1986 and its 1988 presidential hopefuls, will have to contend with this platform in the future, one way or another.

Many Republicans in Dallas were distressed by the platform's social planks because they reminded them of lost opportunities to broaden the party's base below the presidential level in the past -- most recently in 1968 and 1972, when many culturally conservative Democrats voted for George Wallace and Richard Nixon because they believed the national Democratic party, controlled by liberals, condoned if it did not actually encourage, the social upheavals of the '60s and '70s.

"We could have gotten a lot of those Wallace supporters," a Reagan-Bush southern coordinator said in Dallas. "But they weren't from the proper social stratum. A lot of Republicans are more interested in social prerequisites than party building." Others in the party see a clash between what one calls the older, traditionally conservative "populists" and the younger social "libertarians."

"I think 1980 was the heyday of traditional values, because the older conservatives are dying off," one of them said. "As they become fewer they become more strident in insisting they're the majority."

Thus the planks calling for constitutional amendments against abortion and in favor of prayer in the schools and the one rejecting the ERA are potential barriers to winning many to the party. So is the influence of the evangelical Christians.

Jesse L. Jackson, with his references to "Hymies" and his friendship with Minister Louis Farrakhan of the Nation of Islam, has alarmed and angered a great many Jews, giving the Republicans another opportunity to broaden their party's base. But it may be that those who are next most alarming to Jews are some of the party's newly favored evangelicals.

Black voters are lost to the GOP almost completely for the foreseeable future. Hispanics are a growing power in the megastates of California, Texas and Florida, and the Republicans are working to win and hold a respectable minority of them. The party also has a problem with women right now.

One of the things many Republicans most like about their party is its relative ethnic and ideological homogeneity. But when they aspire to be the majority problem, that's also an obvious problem, and the party can't afford to miss too many more opportunities.