As Jose Francisco Cardenal told the story, a young Nicaraguan rebel troop leader tilted his chair a bit too far back as he was waiting for Commander Enrique Bermudez to return to a rebel office in Honduras one day in late 1983.

He fell against a filing cabinet, and one of the drawers popped open. It was full of cash.

The troop leader had come with other field chiefs to complain to Bermudez that despite the continued flow of U.S. aid, their men were down to one meal a day and had no boots. When Bermudez walked in, Cardenal said, he refused to explain the stacks of bills except to deny that they belonged to him or to the rebels, known as contras. Instead, he demanded to know who had opened the drawer.

This tale is significant chiefly because Cardenal, who said he was the Central Intelligence Agency's first link to the contras, told many similar stories alleging contra corruption after he was expelled from the movement in 1982.

Yet now he has rejoined the rebels, whose military leader is still Enrique Bermudez. Cardenal acted the day after the House voted to provide $100 million in economic and military aid for a renewed contra assault on Nicaragua's leftist Sandinista government.

After five years of on-again, off-again U.S. support, and despite virtually nonstop media attention and Reagan administration praise, the contras and their goals and motives remain something of a puzzle.

Critics have charged that they and their troops are guilty of military incompetence and squabbling, cash theft, drug trafficking and brutal human rights violations.

The administration has defended them as "freedom fighters" in one debate after another over the last four years, promising reform, molding the contras into the shape that finally won House backing June 25. The Senate is expected to agree next month.

To succeed, administration officials say, the contras' shaky coalition, the United Nicaraguan Opposition (UNO), must not only to live up to its name but also draw in more of the splintered opposition and allow new leaders to emerge. It will have to inspire hope and loyalty among thousands of ordinary Nicaraguans who would be punished by the government for helping the rebels.

If the Senate approves the aid package as expected, the contras will still head into battle with most of the critics unconvinced and probing for new damaging evidence.

The General Accounting Office will issue a final report in September on what happened to the $27 million in nonlethal aid Congress provided the contras last year. The Senate Foreign Relations Committee is expected to vote shortly on whether to open a full-scale probe of charges that contra officials have used drug-running money to finance their operations during the two years when Congress was providing no military aid.

A crucial number of supporters also say they will jump ship if any hard proof turns up.

"They've got to toe the mark," said House Minority Leader Robert H. Michel (R-Ill.) in an interview. "We have to begin seeing some leadership, some second and third tiers of people . . . and we don't want any instances of any kind of inhumane treatment" of civilians.

Corruption charges were mostly "flimflam," Michel said, but added, "still, every dollar has to be accountable and accounted for."

UNO promised to name a six-member "blue-ribbon panel" of accountants, lawyers and business administrators to oversee the flow of its new money, and the aid legislation calls for a five-member commission of notables to do the same thing.

"We have requested publicly that we be investigated and we welcome all congressional inquiries, and press inquiry too," said Arturo Cruz Sr., 63, a former banker and the most popular in Congress of UNO's trio of U.S.-educated leaders.

The most thoroughly probed of the contra activities was how the $27 million was spent that Congress voted last year for food, medicine, clothing and other "nonlethal" overt aid. News reports focused on tiny stores in Honduras where agents for the contras said they had bought thousands of dollars worth of clothes or equipment, although the store owners said they had supplied and received nothing.

At the request of the House Foreign Affairs subcommittee on Western Hemisphere affairs, the GAO subpoenaed the agents' bank accounts and reported that many checks had gone to the Honduran armed forces, obscure corporations and offshore bank accounts, not to the stores. The GAO said the fate of about $14 million would never be known for sure.

Subcommittee Chairman Michael D. Barnes (D-Md.) called the findings "shocking" and said they raised questions about the way new aid would be handled. But the State Department counterattacked with explanations for many of the checks, charging that Barnes' staff had barred the GAO from showing State the documents or asking for explanations before Barnes held his splashy public hearing.

Robert W. Duemling, head of the Nicaraguan Humanitarian Aid Office (NHAO), which ran the program, said last week that losses to corruption, bribes or theft amounted to no more than "tiddlywinks."

According to his final tally, 35.8 percent of the money, "by far the largest part," bought food. Medical supplies took 22.9 percent, clothing 14.8 percent, transport 9.9 percent and vehicles -- including trucks, boats and airplane parts -- 5.4 percent of the funds, he said.

Another 11.2 percent, listed under "miscellaneous," bought construction materials, agricultural tools, office supplies and such minutiae of daily life as soap and matches, Duemling said. It also provided $140,000 for administrative costs, about 0.5 percent of the total.

Adolfo Calero, 55, a U.S.-educated businessman and the most controversial of the UNO triumvirate, said the contras' 20,000 men are "pretty well off" in basic equipment.

Calero said the contras will work to open a strong military front in southern Nicaragua, where internal squabbles and Costa Rican reluctance to cooperate have prevented much rebel activity.

The Southern Opposition Bloc (BOS by its Spanish initials), itself a coalition of fragments, recently signed an agreement of cooperation with UNO after lengthy talks in Miami. Regional military Commander Fernando (El Negro) Chamorro is among the most capable contra soldiers, according to Defense Department assessments.

"Traditionally successful revolutions in Nicaragua have started in the east and moved west," Calero said, noting that he brought 19,000 people to a Conservative Party rally against the Sandinistas at Santo Tomas, 120 miles southeast of Managua, in January 1981.

Calero, formerly manager of Managua's Coca-Cola plant, was educated at Notre Dame and Syracuse University. He was jailed three times by dictator Anastasio Somoza for helping with labor stoppages as a leader of the conservative opposition.

A former high-ranking Democratic administration official, echoing charges from Cardenal and other former contras, said "it is an open secret" that Calero kept the CIA informed during that period about the anti-Somoza effort, and stayed in touch with its agents after the revolution.

Asked about his CIA ties, Calero said, "In Nicaragua, people who have graduated from U.S. universities, who speak English, who enjoy a certain economic and social position, are friends with the top personnel of the U.S. Embassy" and many other embassies. "Sure, we used to talk about many things . . . . If you want to look from general associations to special ones, go ahead. But I never needed any money from anyone."

Calero stayed in Managua for three years after the revolution, leading the opposition Conservative Party, until his property was confiscated in January 1983. In February he announced he had joined the Nicaraguan Democratic Force (FDN), the largest rebel group, and shortly afterward he replaced Cardenal as its head.

"Calero was imposed by the CIA," Cardenal said before his reconversion. Calero denied that, noting that Cardenal had asked him to join the FDN two years earlier.

Calero has repeatedly said that Bermudez, 53, will remain the contras' military supreme commander despite repeated allegations of corruption from Cardenal and other former rebels. As the most enduring of all the contra leaders, Bermudez and his talents will be pivotal to contra success.

One of the most senior officers of Somoza's National Guard, Bermudez rose from poverty to become military attache in Washington during the last three years of Somoza's government. Supporters say that meant he was in exile as a dangerous critic; opponents say it meant he was trusted to seek U.S. military aid for Somoza.

After the Sandinista revolution, Bermudez got Argentine military government funding to form the "15th of September Legion" that carried out assassinations and sabotage inside Nicaragua. In 1981, that group became the nucleus of the FDN.

That fall, President Reagan signed a secret National Security Decision Directive authorizing the CIA to use existing rebel forces to harass Sandinista supply lines to leftist guerrillas in El Salvador, and Bermudez has headed the contras' military effort since then.

Of the 13 top rebel commanders, including Bermudez, eight are unquestionably former officers of the National Guard that all the current contra political leadership once called butchers.

An Arms Control and Foreign Policy Caucus staff report dated last March says four more commanders are also ex-Guard officers, but FDN officials said the four have long since been expelled. The State Department says 27 percent of the contras were National Guardsmen, 20 percent were formerly Sandinistas and 53 percent were civilian peasants, urban workers or students.

Alfonso Robelo, 47, a chemical engineer, is considered the most decisive and militarily savvy of the three UNO leaders and the only one with significant political following inside Nicaragua. At a news conference, he said UNO was well aware of the skepticism about its ability to meet expectations.

"This is a challenge for us," he said. "We are going to take it and we are going to show results."