Opposition political billboards are cropping up along Managua's streets and highways these days. In many nations, such posters are common. But in Nicaragua, where the Sandinistas have had a virtual monopoly on propaganda in recent years, they are a startling sight.
Now the Sandinistas must decide whether to back up their provision for such displays of political pluralism with truly free elections.
Last week the main opposition parties announced they would not participate in elections scheduled for Nov. 4 unless the Sandinistas met nine political conditions. This week informal talks are under way between Nicaragua's leaders and the key opposition political, business, and labor groups.
One opposition leader says there is ''a better than 50 percent possibility'' that the Sandinistas will make some concessions in these new talks in order to draw the opposition into the electoral process. Sources close to the Sandinistas yesterday told this newspaper that such concessions are possible, but they expressed concern that some of the more conservative members of the opposition might not agree to anything less than their full set of demands.
The concessions the opposition leader and those close to the Sandinistas referred to involve restoration of the rights of habeas corpus and the right of the press to criticize the government for food shortages. The opposition also demands that the government end its law allowing the arrest of anyone who ''reveals political secrets.'' Also under discussion is the possibility of a ''predialogue'' between the Sandinistas and the opposition.
However, nothing has been decided since the Sandinistas have not yet made concrete offers on the opposition's demands. The opposition itself ''has made no internal decisions'' on what their minimum demands for participation should be, says Arturo Cruz Porras, the man tapped as the opposition's potential presidential candidate.
The Social Christians, perhaps the most important party in the ''Coordinadora'' - the coordinating committee of the main opposition's political , labor, and private sector groups - are the most anxious to come to an arrangement with the Sandinistas.
Meanwhile as part of the effort to put international pressure on the Sandinistas to conduct free elections, exiled Nicaragua opposition leader Eden Pastora, Alfredo Cesar, and Arturo Cruz Sequeira (the son of Arturo Cruz Porras) left for Europe Tuesday to round up support of Socialist International leaders. Arturo Cruz Sr. says he fully supports the mission and emphasizes that Pastora has pledged to drop his guerrilla war against the Sandinistas if free elections take place.
Although the Sandinistas may make some concessions, it would be difficult for them accept all of the opposition's demands. The Sandinistas may view a full acceptance of the demands as:
* A shift of the purpose of the Nicaraguan revolution.
* A move that could aggravate political differences within the Sandinista leadership.
* A step that could lead to embarrassingly low level of votes cast for their Sandinista National Liberation Front (FSLN).
The top Sandinista leaders may not agree on whether the their revolution should follow orthodox Marxist-Leninist models, but they seem to be united in a desire to have a revolution that produces a profound redistribution of social and economic power.
It is their deep belief, a belief they will express to anyone who talks to them at length, that those who have most to lose from such profound social and economic changes - the well-to-do private sector and its political allies - will resist them to the utmost.
Thus, the Sandinistas say, the FSLN must keep the reins of power in its own hands to prvent the revolution from being destroyed by the private sector. They say the private sector is allied to and manipulated by the conservative Reagan administration in the US, which they think wants to destroy the Nicaraguan revolution.
Thus, the Sandinistas view with suspicion any talks that could lead to power-sharing with the opposition.
While some of this reluctance is based on a normal, self-centered desire to hold power, Western diplomats agree that ideological considerations play an important role in Sandinistas' reluctance to negotiate away any of their authority.
However, many Western diplomats and Nicaraguan observers feel that the Sandinistas are beginning to realize that in order to reduce US pressure and have an economy that functions well, they will have to share some power.
The question Sandinista leaders must consider, these analysts say, is how much power-sharing is too much. More specifically, they must decide what is the bare minimum of power-sharing they can get away with.
Nicaraguans who are in close contact with FSLN leaders say the Nicaraguan leaders have been impressed with the new energy the nomination of Geraldine Ferraro and the San Francisco convention have injected into Walter Mondale's candidacy for the US presidency.
The Sandinistas, they say, may hold off making any substantial concessions to their internal opposition or to the US until it becomes clear whether the Republicans or the Democrats will win in November.
In the case of a Democratic victory, which until recently the Nicaraguans wrote off as improbable, the Sandinistas might wait and see just how much the new administration would demand as a price for peace. The attention given Central America by the Democrats at the convention and, above all, the congressional cutoff of aid to the contrasm has produced a Sandinista wait-and-see attitude.
The Nicaraguan elections have already caused some tension between the Ortega brothers (junta leader Daniel Ortega is the Sandinista candidate for president while his brother, Humberto, heads the armed forces) and their main rival for power, Interior Minister Tomas Borge.
Western diplomats and some politically prominent Nicaraguans believe that any moves toward a rapprochement with the opposition could lead to problems with Sandinista radicals led by Borge.
Originally, the Ortegas favored holding elections more than Borge. But once an election plan was adopted, Borge decided that he, as the most senior and charismatic of the directorate members, should be the Sandinista presidential candidate.
According to a senior member of a left-wing party allied with the FSLN, Borge approached the Nicaraguan Communist Party and asked it to nominate him for president even after the directorate had nominated Ortega.
Nothing came of this. The Communists reportedly thought Borge would not have accepted their nomination, but would have used such a nomination to show his fellow FSLN leaders that he had widespread support.