With Central America looming as the dominant foreign policy issue of the 1984 presidential campaign, Democratic candidates are beginning a talent search for expert advisers to provide ideas and strategies to challenge President Reagan's controversial approach to the region.

Although the effort is in its early stages, a small group of former government officials and academicians is emerging as the nucleus of the brain trust that eventually will frame the Democratic alternative to Reagan's tough, anti-communist views on Central America.

Some are acting as informal advisers and consultants to two or more of the six declared Democratic candidates. The two regarded as front-runners, former vice president Walter F. Mondale and Sen. John Glenn (D-Ohio), appear to be in increasing competition for the same people

Most of these experts are unknown outside the circles of diplomacy and Latin American scholarship. But many, among them Viron P. Vaky, Lawrence A. Pezzullo, Wayne S. Smith, Sally A. Shelton and Robert Pastor, helped shaped the Latin American policies of the Carter administration.

They are regarded by Republican conservatives as the people whose liberal, human-rights-oriented approach was responsible for "losing" Nicaragua to the Sandinista government and for allegedly emboldening Cuban President Fidel Castro to support leftist guerrilla movements in El Salvador and elsewhere in Central America.

For that reason, the Democratic and Republican platforms seem likely to take radically different approaches to dealing with the chronic instablity of Central America and the Caribbean.

Now, however, many Democrats privately concede that their party's candidates are hesitant, reflecting divisions apparent in congressional Democrats' inability to forge a united front in responding to Reagan's Central America tactics.

Congressional Democrats have engaged in considerable hand-wringing about such situations as increasing military aid to El Salvador, soft-pedaling continued human rights violations and providing covert aid to Nicaraguan rebels.

However, they have avoided confrontation with the administration and have relied instead on temporizing compromises and legislation filled with loopholes through which administration policy-makers have maneuvered easily.

Factors leading to this lack of consensus include:

Generational differences between older Democrats reluctant to depart too far from traditional bipartisanship on foreign policy and younger Democrats, who view Central America as a potential replay of Vietnam.

Regional differences rooted in perceptions of the problem that geographic proximity to Central America and economic interest spark among northern and southern Democrats.

Perhaps most pervasive of all, concern that Democrats might misjudge public apprehension about Reagan's course and play into his hands next year by setting themselves up as targets of a potential "Who lost El Salvador?" campaign.

So, the Democratic candidates have approached Central America gingerly, knowing it is a major but unpredictable issue. Last week, for example, Glenn felt compelled to dispute publicly a Washington Post report that interpreted one of his speeches as appearing to narrow his differences with Reagan on Central America.

Sen. Alan Cranston (D-Calif.) is trying to broaden his credentials by visiting Central America. Sen. Gary Hart (D-Colo.) soon will do the same.

Hart appears to have staked out the clearest challenge to Reagan by advocating the freezing of U.S. military aid and troop levels in the region. The other candidates are more cautious.

In public statements, all of them have opposed U.S. support of covert action against Nicaragua and have called for more emphasis on negotiations instead of military measures.

But, while their tone and stress vary, they essentially support such fundamentals of Reagan policy as continued military aid to El Salvador and increased economic aid for the region.

One expert consulted by Mondale and Glenn said, "When you sift out the rhetoric, there's a big element of 'me-tooism' in what the Democratic candidates are saying. There are a few things that they can safely say they're against. But they have yet to say with any real specificity what they would do differently than Reagan."

With increasing pressure on the candidates to do precisely that, there is growing interest in those providing them with ideas. Since Mondale and Glenn are regarded as the front-runners, most attention has focused on those with whom they have been talking.

In addition to consulting the usual range of party elders and leaders of Congress as well as groups involved with the region, both have been compiling lists of experts who might serve as consultants.

In the Mondale camp, Robert Pastor, who handled Latin American affairs while on the National Security Council staff in the Carter administration, is reportedly drafting position papers. Glenn has Curtis C. Cutter, a former foreign service officer with extensive experience in Latin America, working to recruit an advisory team.

Both campaigns appear to be trying to tap essentially the same talent pool. It includes, for example, such academicians as Jorge Dominguez, a Cuban-born Harvard professor and Caribbean expert, and Wayne Cornelius of Stanford University, who is widely regarded as the country's preeminent scholar on Mexico.

Names mentioned most frequently by both campaign staffs are those of people who had key roles in Latin America policy-making under President Carter.

They include Vaky, assistant secretary of State for inter-American affairs for about half of Carter's tenure; Pezzullo, ambassador to Nicaragua before and after the Sandinista takeover; Smith, the former head of the U.S.-interests section in Havana who resigned from the foreign service to protest what he charged was the Reagan administration's inflexible attitude toward Cuba; Shelton, who served Carter as a deputy assistant secretary of State for Central America and ambassador to several small Caribbean countries, and Ambler Moss, a former ambassador to Panama.

All had a part in formulating the approach to Central America taken during the latter part of the Carter administration after the Sandinistas came to power in Nicaragua and the guerrilla challenge grew in El Salvador.

The approach centered on El Salvador, and its main emphasis involved supporting the government and armed forces against the insurgents while trying to prod them toward democratization and ending human rights abuses.

Reagan inherited this policy and has repeatedly claimed that his actions in Central America are a continuation of what began under Carter.

That is disputed by most Carter-era veterans. They charge Reagan has deviated significantly by emphasizing the military side of the Salvadoran problem at the cost of reform, taking an overly confrontational attitude toward Cuba and Nicaragua and exiling virtually all foreign service personnel who worked on Latin policy under Carter.

Some have been outspoken in criticizing aspects of Reagan's policy. But, like the candidates soliciting their views, they have been less clear about what they would do at the controls. Probaby some will soon get a chance to spell out their ideas.