Banners flying over the streets of Managua proclaim ''No Pasaran'' (they shall not pass).
The slogan echoes a rallying cry of Spanish Republicans when Madrid was surrounded by fascists during the Spanish Civil War.
Nicaragua's Sandinista leaders aren't worried about Spanish fascists. They are concerned that rightist followers of the dictator they deposed in 1979 and individuals they call ''lackeys of the (United States) Central Intelligence Agency'' may soon try to unseat them.
In fact, government leaders have announced that ''the counterrevolution has begun.''
This so-called contra (counterrevolution) is a joke among cynics, but interviews with Nicaraguans here indicate that it is also a hope among many who are discontented with the Sandinista leadership.
The contra is clearly a hot topic at dinnertables and sidewalk cafes. But generally, ''when the contra comes'' emerges as a point of reference for the future - one that will probably not arrive in one's lifetime. Most Nicaraguans decline to discuss revolution seriously. No one, it seems, openly admits to participating in it.
One's position toward the counterrevolution seems to be determined by politics and personal experience.
A Managua merchant says: ''They say the counterrevolution is coming. I hope so - otherwise we're going to die of hunger.''
Mothers say they don't want their sons to become involved in another war. Some of the sons, too, claim they are tired of fighting.
''I fought for three years during the insurrection and injured my leg,'' says a sturdy, bronzed banana worker from Masaya. ''I don't want to do it again.''
Staunch Sandinista supporters and the military scoff at the idea that the contra could destroy their revolution. Ask almost any soldier what he thinks of Eden Pastora Gomez - the revolutionary war hero who now leads a movement against the Sandinistas - and he'll snap, ''Traitor!'' Ask if he thinks the contra will amount to anything, and he'll retort, ''Never!''
A measure of government worry about an uprising was seen in a recent parade marking the fifth anniversary of the Popular Militia. Soldiers chanted ''What is the mark of a traitor? A follower of Eden Pastora.''
Neighborhood Sandinista Defense Committee members say they would never allow any move against government leaders to go too far.
''We fought before, and we'll fight again,'' declares spirited Managua grandmother Eva Chavez. ''We have rifles. They'll have to kill us first.''
But there are at least some malcontents who vocally oppose the Sandinistas. When a Sandinista youth leader approached an unemployed carpenter recently to discuss the revolution, the carpenter shouted:
''The only one who gave me work was Alfonso Robelo (Callejas). !Viva Eden Pastora!'' Mr. Robelo is a businessman and former junta member who has joined forces with Mr. Pastora against the Sandinistas.
A measure of revolutionary rhetoric has also penetrated into Nicaraguan theater. A recent romantic comedy in Managua, called ''The Six O'Clock Train,'' has a very political subplot. In one act, a CIA agent, Uncle Sam, the editor of the opposition newspaper La Prensa, an archbishop, a member of the Permanent Commission on Human Rights, Mr. Robelo, and Mr. Pastora - flanked by two sleazy-looking women - meet at a secret location on the Costa Rican border to plot strategy. The characters are depicted as complete fools. The audience loves it.
The contra and Mr. Pastora are viewed as one and the same here. Yet support for the flamboyant commander is difficult to gauge.
A university professor who gave a lecture at a milk factory on the day Mr. Pastora announced he would oppose the Sandinistas says:
''I was a little afraid when Pastora dropped the bomb, because he was such a respected worker,'' she explains. ''But during the meeting, some guy stood up and said, 'I never thought Eden Pastora would lower himself to this!' He had an identification card with Pastora's signature on it, which he proceeded to burn. Pretty soon, everyone else was doing the same.''
Public response on the Atlantic coast, or at least in Puerto Cabezas, apparently was more supportive. A former resident of that city who now lives in Managua explained the reaction in her hometown:
''I was in Puerto Cabezas the day that Eden made the announcement,'' she remembers. ''Everyone was so happy. They were yelling, 'Now he's on our side.' ''
No one doubts some sort of counterrevolution exists. But no one knows if it is a serious threat, since communication with the Honduran border, where skirmishes between Sandinistas and guerrilla opposition are occurring, is limited.
But the memory of war is too fresh for many to be willing to support it where they live.
A store owner in one of Managua's poorest barrios says: ''Yes, I suppose that I would fight against the counterrevolutionaries. But I wouldn't do it for the government. I'd do it for my family and my ancestors.''