With the approach of the congressional vote on funding of Nicaraguan rebels, the Sandinista government has hosted an array of visiting U.S. lawmakers, former officials, artists and journalists in an effort to swing the vote its way.

Twenty-one senators and congressmen have been greeted by Foreign Ministry officials and stifling April heat at Managua's Augusto C. Sandino Airport since Easter Sunday. Many appear to have confirmed the positions they came with, although at least two have indicated possible switches on the issue of a $14 million appropriation, to be voted upon today, destined for the anti-Marxist rebels.

Other visiting Americans have included former aide to president John F. Kennedy, Theodore Sorensen; president Jimmy Carter's CIA chief, Stansfield Turner; former Newsweek magazine editor William Broyles and actress Darryl Hannah, famed as the mermaid in last year's movie "Splash."

Some congressmen and senators have traveled around the country, receiving military briefings, visiting resettlement camps in the embattled northern mountains and talking to rebels who have accepted a government amnesty. The Americans have had long interviews, and in some cases steak dinners, with President Daniel Ortega, Foreign Minister Miguel D'Escoto and other Sandinista officials.

The visitors also have met with opponents here of the Sandinistas, including the leaders of opposition parties, Managua's Archbishop Miguel Obando y Bravo, and directors of the censored opposition La Prensa newspaper.

According to legislators interviewed and also Foreign Ministry officials privy to the talks, a main contention made by Ortega is that Nicaragua does not and will not belong to the Soviet camp. The Sandinistas have stressed that they do not represent a military threat, as the Reagan administration charges, and that if the rebels encouraged by the United States end their war, normal U.S.-Nicaraguan relations would follow.

Rep. James Traficant (D-Ohio) quoted Ortega as saying "that if he wears a uniform, the Reagan administration compares him to Fidel Castro, and that if he wears a three-piece suit, they say he's like Soviet leader Mikhail Gorbachev."

Many of the legislators said they expressed concern about press censorship, problems of the Roman Catholic Church hierarchy and the private sector, and about a growing number of Nicaraguans sentenced to prison terms by military tribunals for war-related crimes.

On Saturday, Democratic senators John F. Kerry of Massachusetts and Thomas R. Harkin of Iowa returned to Washington with a Sandinista offer to limit press censorship and amplify other civil liberties in exchange for an end to the war. U.S. officials responded Sunday that the offer contained nothing new.

"They say stop the war and there will be changes," said Rep. Bob Edgar (D-Pa.), earlier in the week. "Why don't we stop the war and see if what they are saying is true."

Edgar, a Methodist minister, was part of a delegation that talked for almost three hours with Foreign Minister D'Escoto, who is a Maryknoll priest suspended by the Vatican earlier this year for ignoring a Vatican ban on priests in government. He talked to the American clergymen of his religious vocation, its relation to his commitment to the Sandinista cause and his hopes for peace. Edgar said he found the foreign minister's explanation "sincere" and "moving."

More conservative congressmen were not as impressed with the Sandinistas.

"All they do is blame the United States for everything," said Rep. Robert Livingston (R-La.), who said he had backed President Reagan's policy in the past and had not changed his mind during his visit. "As far as I can see, the contra rebels are the only thing that has made these guys want to talk to us at all."

David McCurdy (D-Okla.), who has voted against funding of the contras in the past, visited a partially constructed Sandinista air base at Punta Huete, 20 miles from Managua.

Reagan administration officials have warned that the airfield could be used in the future by Soviet aircraft, while the Sandinistas insist that the base is purely defensive in nature.

McCurdy said he saw 10,000 feet of concrete runway, more than is necessary for defensive interceptors, and also revetments to house and protect planes from attack. McCurdy said the airfield did not appear defensive and was out of step with attempts to achieve peace in the region.

"It's an awfully permanent-looking facility when we are talking about demilitarizing Central America," he said.

At a press conference on leaving Nicaragua, McCurdy did not say he had changed his vote, but he did say he had reached a new perspective. "I believe the contra have had an impact, and that the Sandinistas are modifying their direction, modifying their behavior in response to that threat," he said.

Rep. Tom Robinson, a freshman Democrat from Arkansas, arrived telling journalists he had not decided how to vote, but described himself as a "boll weevil" southern Democrat who had backed the president on the recent MX missile vote and suggested that he would probably do so again.

Two days later, after meeting with Sandinista officials and after a trip to a resettlement camp in the department of Esteli, Robinson said he would support humanitarian aid to the rebels but not military aid.

"I met a 28-year-old woman with nine children in that camp. I saw that the concrete that was being used to build new houses was from Havana and that the trucks that were helping were from the Soviet Union. Her kids will probably grow up thinking that the Cubans and the Soviets are the good guys and we are the bad guys. There's something wrong there."

Robinson described the Sandinistas as "young, smart, canny" and said he was impressed by them, but also worried about their Marxist-Leninist leanings.

Nonetheless, he said he saw no immediate threat from the Sandinistas and for that reason, mainly, would not support continued military aid.

"I think we might be better off with a cooling-off period and give Mr. Ortega a chance to decide where his government is going," said Robinson. "I have changed my mind on that. I just don't see the military threats people talk about. We could take care of these guys any day of the week."