Sandinistas march in step. Nicaraguans say hot debate on peace plan ended in consensus. Central America: search for peace.

``A division in the FSLN - certainly the enemy's most persistent dream - is and will be impossible.'' Nicaraguan Interior Minister Tom'as Borge Mart'inez could not have been more blunt as he celebrated the ruling Sandinista National Liberation Front's (FSLN) 26th anniversary here last week. Rumors that the nine-man party leadership was split, he said, were the product of ``desperation and emptiness'' among the opposition.

Mr. Borge's confidence in Nicaragua's uniquely collegial system of power seems well founded, foreign diplomats and opposition politicians here say. Nonetheless, several of them note, the government's decision to open indirect cease-fire talks with contra leaders surprised party members, and has met with some grassroots resistance.

Recurrent speculation about divisions among the nine members of the FSLN's National Directorate has surfaced many times over the past eight years. The group is comprised of three men from each of three Sandinista factions that united only months before their 1979 revolution.

Most recently, as Managua plots its course through the maze of Central America's peace treaty, the rumors have fed on apparent differences between speeches by Comandante Bayardo Arce Castano, a directorate member, and President Daniel Ortega Saavedra.

Late last month, Mr. Arce, often portrayed as a ``hard-liner,'' set forth the limits to Sandinista concessions under the region's Esquipulas peace pact.

A few days later, Mr. Ortega, often cast as a ``pragmatist,'' announced an important new concession, indirect talks with rebel leaders to end the six-year war.

Government officials, however, were quick to point out that Arce had not ruled out negotiations on a cease-fire, only on a ``political dialogue'' with the contras. In fact, the Sandinista Assembly meeting that Arce addressed had privately approved indirect talks with the contras earlier that day, say Assembly members. The 105-member Assembly is the Sandinistas' top consultative body.

``Nothing Arce said contradicted anything Daniel said later,'' said a top Sandinista. ``It was just a matter of tone and emphasis. Decisions in this revolution are made by consensus.''

Party militants say the strain and complexity of the peace process have provoked intense debate among the leadership, but it has ended in agreement.

``The National Directorate sometimes decides domestic policy by majority vote, almost never has to do so on foreign policy, and hasn't needed to vote once on the Esquipulas process,'' says an official familiar with the decisionmaking process. ``Dole Republicans and Reagan Republicans are more divided than the FSLN leadership.''

That impression is shared by Western diplomats who monitor Sandinista Front politics.

``Ortega would never have stood up and announced such a contentious policy without having the other eight comandantes behind him,'' says one European diplomat. ``Especially if he knew that people further down the party structure would find it hard to accept.''

The President's announcement Nov. 5th was met with a baffled silence from his audience of 30,000 supporters in Revolution Plaza, who clearly had not expected such a policy reversal.

Since then, one Western envoy says, ``middle level party cadres have privately expressed concern to diplomats that maybe the leadership has gone too far.''

Since President Ortega signed the Esquipulas accord on Aug. 7, members of the ruling party say, the Sandinista Front has devoted innumerable party teach-ins, seminars, official press, and speeches to explain policy, and to convince skeptics that treaty requirements don't compromise revolutionary principles.

The Sandinista Assembly, which normally meets twice a year, has held two special sessions in the past three months to discuss the leadership's policies.

``We have to explain difficult things to the people ... because the people have to understand these steps in order to support them,'' said Vice-President Sergio Ram'irez Mercado. ``People here adapt themselves very quickly to new situations.''

``The National Directorate is not worried about any abyss opening up between them and the militants,'' says a top Sandinista intimately involved in explaining policy to the masses.