When the revelations of a top-level Nicaraguan defector rocked Washington and Managua recently, Robert Kagan and Cris Arcos were at the center of the administration's attempt to capitalize on what the Sandinistas have called their "most important betrayal."

The two officials, who are key players in the administration's high-pressure public relations campaign to keep aid flowing to the Nicaraguan contras, guided the unveiling of the defector, Maj. Roger Miranda Bengoechea, and their offensive succeeded. It was helped, in the end, by a bit of luck, and was engulfed in the controversy that accompanies almost all debates on Central American policy.

Kagan is a deputy and close adviser to Assistant Secretary of State Elliott Abrams, a leading and controversial proponent of the administration's contra program. Kagan's specific duties include supervising State Department press specialists on Central America and helping lobby for contra aid legislation on Capitol Hill.

Until recently, he also headed the Office of Public Diplomacy for Latin America and the Caribbean, designed to promote the administration's Central American policy. Congress last month abolished the office after activities conducted under Kagan's predecessor came under criticism in connection with the Iran-contra affair.

Arcos, whose title is coordinator for public diplomacy on Central America at the White House, is the top contra expert on the staff of White House communications director Tom Griscom. Arcos advises Griscom and other White House public relations officials on the status of the contra program and efforts to win public support on Capitol Hill and elsewhere.

When U.S. intelligence officials completed their long debriefing of Miranda, a former top aide to Nicaraguan Defense Minister Humberto Ortega, and senior policymakers decided Miranda was ready to go public, the job of executing that sensitive task fell to Kagan. Kagan in turn sought assistance from Arcos, a career U.S. Information Agency employee with extensive experience in Central America.

Kagan and Arcos knew that some previous attempts to capitalize on allegations from defectors had backfired and turned into public relations fiascos. In 1982, for example, a captured Nicaraguan youth, who U.S. officials claimed would confirm Nicaraguan and Cuban support of Salvadoran guerrillas, recanted his allegations at a Washington news conference as startled U.S. officials stood by.

Kagan and Arcos also expected Capitol Hill critics of the contra program to attack Miranda's credibility and accuse the administration of timing his revelations to coincide with last month's crucial congressional vote on continuing contra aid.

Kagan and Arcos talked to Miranda at length, and received assurances about his credibility from U.S. intelligence officials.

Then, in a decision that drew the ire of many members of the Washington press corps, Kagan and Arcos decided against presenting Miranda to the American public through an open, full-fledged news conference. Instead, they limited the first Miranda interview to reporters from four news organizations: the Associated Press, The New York Times, Time magazine and The Washington Post.

Their goal was to avoid a circus-like atmosphere, they said, and to ensure that Miranda's first exposure to the news media would be orderly.

The first interview was conducted in a conference room at the State Department and went on for more than four hours. Miranda conducted himself in a calm, low-key manner, and officials were pleased that it went off without a hitch.

But, as has been previously reported, the big break came when the Nicaraguan defense minister publicly confirmed key parts of Miranda's account about Sandinista plans for a major, Soviet-backed military buildup over the next seven years.

Suddenly, Miranda seemed to be everywhere. Within a week's time, he gave about 60 press interviews and, under Kagan's auspices, was paraded around Capitol Hill for numerous meetings with members of Congress.

While Miranda may not have been the chief reason Congress recently approved an additional $8.1 million in contra aid, congressional staff members said Miranda certainly made the administration's job easier.

"A number of people have commented," said Abrams, "that the handling of Miranda when he was made available to the press and to the Congress has done a great deal to enhance his credibility."

Kagan and Arcos come to the Central American issue from sharply different backgrounds.

Kagan, 29, is a political appointee, a loyal Abrams aide, whose aversion to the Marxist-Leninist policies of the Sandinistas stems from a world view developed in academic and intellectual circles. He has been influenced by the arch-anticommunist views of leading neoconservative political thinkers.

A 1980 graduate of Yale, where he majored in pre-World War I European history, Kagan went on to be an assistant editor at Public Interest, a New York-based, political journal coedited by Irving Kristol, a leading neoconservative figure. Kagan later spent two years at Harvard's Kennedy School of Government, and served briefly as a foreign policy adviser to Rep. Jack Kemp (R-N.Y.) before joining the State Department in 1984. His duties have included serving as a speechwriter for Secretary of State George P. Shultz and a brief stint at USIA.

He became an assistant to Abrams in November 1985, and, among other things, played a central role in pushing for reforms within the contra movement that led to a broader-based political leadership.

Arcos, 44, is a career senior Foreign Service officer who served in Portugal, Brazil and the Soviet Union before spending five years as the public affairs counselor for the U.S. Embassy in Honduras, between 1980 and 1985.

A native of San Antonio, Arcos grew up in a Hispanic American family and speaks English and Spanish. He graduated from the University of Texas in 1966 with a degree in government, briefly taught mathematics to poor San Antonio high school students and spent two years in the Army. He later received a master's degree from Johns Hopkins School of Advanced International Studies before joining USIA in 1973.

During a two-year tour as a press and cultural aide stationed in Leningrad, Arcos said, he was struck by the warmth of the Soviet people but was depressed by the stifling, totalitarian nature of Soviet society. He said his experience in Russia made him acutely concerned about the Soviet influence over Nicaragua's Sandinista government.

Arcos' tenure at the U.S. Embassy in Honduras was during the period that Honduras became a major center for the administration's contra war. He had regular contact with many of the key U.S. officials and contra leaders involved in the war along with reporters covering it. He also developed close relationships with top Honduran officials.

"The main thing about Cris is that he knew everybody," said deputy national security adviser John D. Negroponte, who was the U.S. ambassador to Honduras during most of Arcos' stay. "He is one of those people who is very gregarious."

"If all else failed," Negroponte recalled, "you could rely on him to effectively communicate with the top leaders of Honduras."

When Congress returns, Kagan and Arcos can be expected to play pivotal roles in the administration's campaign to win congressional approval of renewed military aid to the contras. What Congress decides next month -- in its first direct votes on lethal aid in more than a year -- may help make or break the contras.