The power of the liberal network of congressional and bureaucratic staff aides has been demonstrated again in their apparently successful campaign to bar Leo Cherne, an internationally beloved figure working with refugees, from the Board for International Broadcasting, which governs vital broadcasts to communist Eastern Europe.

Cherne is inclined to reject appointment to the board despite urgings from the White House. This confirms the staff network's hidden power to override top-level government officials behind their backs. It also reflects the policy split over whether detente still ought to be enshrined. Cherne is among those who believe that era has passed, and that U.S. broadcasts must toughen up.

The campaign against Cherne, at 67 a world leader in international rescue and refugee work, was plotted by the BIB's chief of staff, Walter Roberts, working covertly with staff aides of several liberal senators.

Radio Free Europe and Radio Liberty, controlled by the BIB, broadcast to Eastern Europe and the Soviet Union. Both had heavy CIA financing until 1973. The campaign put on by Roberts and the Senate staffers implied, falsely, that if appointed chairman of the five-member board, Cherne would fall under CIA influence.

What really was at stake, however, was whether Roberts, a 63-year-old retired Foreign Service officer, would stay in power. How he and anonymous Senate aides were able to override President Carter's national security advisers in derailing Cherne is testimony to how Washington really works.

Word leaked that national security adviser Zbigniew Brzezinski had asked Cherne to consider appointment as BIB chairman when the term of former ambassador John Gronouski expired in April. Roberts then triggered his blocking operation.

The reason is found in a confidential March 28 memorandum from Cherne to the White House that goes to the heart of what ails Radio Free Europe and Radio Liberty: the BIB. Criticism of the BIB's inability to step up American propaganda to match post-detente requirements runs from failure to increase broadcasting to Soviet Moslem areas near Afghanistan to strain between BIB and the two radios.

No member of the board, Cherne writes, "can more than casually assess operations of the magnitude to be performed" by the two radios. Consequently, the BIB staff's authority is "more than normal or desirable." Cherne's prescription: "The next chairman of BIB must, whatever the resistance from his colleagues who may cherish their distinction and tasks, move to bring the existence of the BIB to an end."

Whether or not Roberts ever read Cherne's memo, he and the rest of the BIB staff surely knew their life-and-death powers over the radios would end under Chairman Cherne.

Roberts was present with staff aides of Sen. Claiborne Pell, chairman of the foreign relations subcommittee overseeing the radios, at a long, unannounced meeting in Pell's office the last week of April. That week, Gronouski's three-year term came to an end (though he continues as chairman in the absence of a replacement).

At the meeting in Pell's office, a letter was drafted to President Carter that took dead aim at Cherne's appointment: "We believe the work of a decade in assuring the professional integrity of RFE/RL would be undone if any of the present members of the BIB were to be replaced by persons who could even remotely be identified as presently or formerly associated with the CIA or intelligence activities in any capacity."

The network was energized. Aides secured the signatures of Pell and three other detentist members of the Senate Foreign Relations Committee: Chairman Frank Church, Jacob Javits and Charles H. Percy.

The letter blackballed Leo Cherne, a longtime member of the president's Foreign Intelligence Advisory Board (now abolished). Roberts had the letter leaked to The New York Times two weeks later. The Times story falsely charged that the International Rescue Committee (then, as now, headed by Cherne) "reportedly received $15,000 in CIA money in the mid-1960s." That raised suspicions that Roberts was the source of the false information.

The strategy of Roberts and his BIB staff was clear: with the support of four prominent senators and the red-herring warning about a return to evil CIA influence, Cherne was a goner.

But at least one senator signed the letter without spotting the booby trap. After the letter leaked last month, a sorrowful Javits said publicly that nobody had told him "of any name" being considered for appointment. "I had not the foggiest notion of any individual, and certainly not Leo Cherne," he said.

Such is the artful way of the staff network, overriding policies of the highest officials, slithering through subterranean corridors of power to gain its ends. The result is bad business as usual, no change in the BIB and no needed improvement in carrying America's message into the Soviet empire.