Nicaragua's new president, Daniel Ortega, who in the cause of the revolution against dictator Anastasios Somoza used to rob banks, is a middle-sized man of 37, with heavy eyebrows, a thick mustache and a chip on his shoulder.

Clad in olive-drab fatigues, he strides into the foyer of the "protocol house" of his shaky, threatened government, surrounded by men in white embroidered cotton shirts, to greet the latest congressional delegation to come to Managua to tell him how to disarm his enemy, the president of the United States, in the matter of continued aid for the contras.

He goes around shaking hands, saying "hola" in a manner so brusque as to make it sounds like a command. He does not smile. He is the angry young man of Latin-American politics.

He takes his place at the top of a circle of large wicker rockers, with the Americans on one side and his men on the other.

The leader of the delegation, Rep. Edward Markey, (D-Mass.) who is also 37, puts a familiar proposition to the president.

Will he, if Congress defeats the president's request for $14 million more for the contras, make some gesture, like lifting restrictions on freedom of the press?

Ortega, the assumed military swagger vanished, keeps his well- kept hands quiet in his lap and listens intently. He speaks in low, uninflected tones at great length, but does not answer the question. He calls the new Reagan "peace" plan "an ultimatum." The press censorship, which like everything else in the country, including the water supply, is erratic, is "an extraordinary measure for an extraordinary situation." He notes that Reagan has violated the freeom of the press when he invaded Grenada.

Ortega, who was educated by Jesuits, seems to want to debate.

Rep. Rick Boucher (D-Va.) asks about the 10,000-foot airstrip that is under construction. He, too, gets a long reply but no real answer. Nicaragua has been invaded five times; it needs interceptor aircraft; the present airport is over a geological fault.

Boucher reminds Ortega that they have met before. Ortega looks blank. The lack of charm seems willful. There is none of the manic animation of a Fidel Castro, no Latin histrionics, no ballet of gestures such as are coming from his loquacious foreign minister, Miguel Descoto, the Maryknoll priest, who is serving as interpreter -- and adding a few flourishes of his own. Ortega's poker face remains expressionless. He does not have a photographic mind, he says.

Theodore C. Sorensen, who was White House counsel to President John F. Kennedy, a young leader of another stripe, changes the subject. He reminds Ortega that when the Sandinistas won in 1979, President Carter welcomed the revolution, with "no hostility, no opposition of any kind."

Ortega, thrown off the track of rehearsed responses, shows some life. He begins to reveal his real problem: He is a grievance collector. He recites U.S. abuses against his country. President Carter is the exception; President Reagan is the rule. "It was easier for President Franklin Pierce to acknowledge as president of Nicaragua the American William Walker (a 19th century adventurer) than it was for President Reagan to acknowledge me."

"The wounds are deep," says Ortega. He does not add that they are personal, too. Both of his parents were jailed for anti- Somoza activities. One of his brothers was killed in the cause. He himself has served seven years in jail, under a warden "trained by Franco."

He wants to be friends with both the United States and the Soviet Union."The Soviets don't tell us how to act," he says pointedly.

Sorensen tries to rouse him from self-pity.

"We won't resurrect Somoza if you don't resurrect Franklin Pierce." "

A trace of a smile flickers over Ortega's thin olive cheeks.

"President Reagan has resurrected Franklin Pierce," he replies.

I inquire if there is a world leader he admires. He is disconcerted, wary. "I haven't thought about it," he says. "Indira Gandhi," he finally mutters. A living hero? He reluctantly mentions Fidel Castro, covers it with a reference to Argentina's President Raul Alfonsin and an obscure Latin- American bishop.

Yes, he has studied the American Revolution, "as we studied all struggles for independence." He volunteers that he has read about Martin Luther King -- and had been struck that "in such a citadel of democracy there was so much discrimination."

He is told that Americans wonder why he doesn't smile more. He understands the question before the translation is made. He grins, he shows dimples.

"I am going to get some advice from President Reagan," he says dryly. "The first thing he does is to throw out a huge smile and then says something. I would feel ridiculous doing that."

Reagan has made the case against Ortega ridiculous by overstating it. Ortega, for all his talk of Marxism, is not sinister. He is in over his head. And he is trying to cope with the present by invoking the past, which is no way at all.