The most surprising foreign policy development of the just-recessed session of Congress--the House's vote last week against "the secret war" in Nicaragua--is a message to President Reagan from the Democratic centrists and the political system at large about the controversial aspects of his Central America policy.

The 228-to-195 vote to cut off undercover CIA aid is also a vivid reminder of the personal and institutional factors that contribute to Washington decision-making, especially on Capitol Hill.

The man behind the vote, in this case, was Rep. Edward P. Boland (D-Mass.), a veteran member of the inner circle of the House, a moderate-to-conservative on most national security issues and, of central importance to this controversy, the chairman of the Permanent Select Committee on Intelligence since its founding seven years ago.

Boland's main argument, which he stated in presenting his cutoff bill, was that "This secret war is bad U.S. policy--because it does not work; because it is in fact counterproductive to U.S. interests; because it is illegal." The ensuing floor debate, which was rated by Capitol Hill reporters as one of the best in a long time, revolved mostly around these issues, pro or con.

In the background, though, was the personal credibility of Boland and the institutional credibility of the Intelligence Committee, whose Democratic members strongly backed their chairman in calling for an end to the undercover U.S. aid.

Boland, 71, has been in the House for 30 years without making waves or headlines. He is so controversial at home that a few years ago he spent a total of $47 on his reelection campaign, a record low for any House member that year, and such a publicity seeker that he does not even place his biography in the Congressional Directory, rarely issues a press release or grants an interview and recently turned away many offers to be interviewed on national television programs about his stand on Central America.

Within the House Boland is considered a serious and powerful figure, but to the public, at least until recently, his profile was so low that by his own admission, "If you ask anyplace else but Springfield, Mass., nobody would even know me."

Before the controversy about the Nicaraguan "contras" Boland was perhaps best known among capital insiders as the close friend and, for 24 years, the Washington roommate of Rep. Thomas P. (Tip) O'Neill Jr. (D-Mass.). During most of that time O'Neill commuted home to Cambridge every weekend and Boland was a bachelor. He married late, 10 years ago, and now flies home to his wife and four young children on weekends.

After being elected speaker of the House in January, 1977, O'Neill was briefed by the CIA top brass every Wednesday morning in Sam Rayburn's secluded "Board of Education" drinking room in the Capitol.

After a few months of hearing secrets he could not tell anyone else, O'Neill decided to turn over the job to a committee of trusted people, lest one of his sleepy solo sessions at 7 a.m. be the basis for an executive branch claim that by consulting him the House had been consulted about some questionable or ill-fated operation in the twilight zone between war and peace.

Set up as a select committee, the intelligence panel's membership is under the personal control of the speaker rather than being subject to party vote. O'Neill used that control to install a group of respected, serious and uncontroversial people.

For the chairmanship O'Neill picked his old friend and roommate, of whom he recently said, "Eddie is so secretive he wouldn't even tell his left hand what his right hand is doing."

Boland, in turn, decided to share the secrets and the responsibility with his fellows and rule by consensus, in all but the rarest of cases bipartisan consensus.

Partly because they share secrets they can't talk about, the intelligence committee has become something of a special club in the House, with most members spending much time in their clubhouse, the tightly guarded Capitol office of the committee, reading classified reports and hearing briefings from officials of the CIA and other intelligence agencies.

Under the post-Watergate Hughes-Ryan law, all secret U.S. intelligence operations must be authorized in writing by the president and presented in timely fashion to the intelligence committees of the House and Senate.

In this way the committees have been informed of dozens of such operations, large and small. In most cases, they have gone along. At other times, although they possess no veto power under law, their doubts or criticisms expressed by letter to the CIA have been enough to cause the questioned operation to be dropped.

Right from the start, Boland and his colleagues were leery of the "secret war" in Nicaragua, and right from the start, the Reagan administration seemed determined to proceed no matter what.

The lawmakers expressed immediate objections when presented in December, 1981, with a plan for a CIA-backed 500-man force to take paramilitary action in Nicaragua. The committee reportedly could not see where the action would lead, especially if it were exposed and if Nicaragua retaliated against Honduras or Cuba came to Nicaragua's aid. Those same questions are being asked today.

Shortly after the initial briefing by CIA Director William J. Casey, a critical letter was sent from Boland. "Nobody disagreed" within the committee, Boland said later.

The CIA proceeded anyway, and in months to come it returned to the committee at regular intervals to report increasingly bold and explosive activity and ever-larger numbers of U.S.-backed guerrillas.

Within two months the 500 men had jumped to 1,000, then to 1,500, then 4,000, then 5,500, then 7,000, then 8,000, now more than 10,000--20 times the original "strike team." Shortly before the House vote the CIA began planning--and Reagan reportedly approved--an increase to 12,000 to 15,000 U.S.-backed rebels against the Sandinista government in Managua.

As the CIA-backed force ballooned in size, its missions and justifications kept changing in bewildering fashion. As publicity increased and apprehensions grew on Capitol Hill and among the public, the intelligence committees adopted, first secretly and then publicly, a limitation known as "the Boland amendment" forbidding the CIA to support guerrilla forces "for the purpose" of overthrowing the Managua government or provoking a military clash between Nicaragua and Honduras.

With Boland's name on the line as never before, the breaking point came when the leaders of the "secret army" invited U.S. reporters to their hideaways in the Honduran-Nicaraguan border area this spring and let it be known that, whatever this strange law in Washington said, their objective was to bring down the Managua government.

At that point, Boland said in a recent interview, "It was no longer a secret war anyway, it was open. It was almost like a rogue elephant, doing what it wanted to."

With the concept that the intelligence committee functioned as representative of the House to oversee secret operations on its behalf, Boland said, "We had a responsibility to the House . . . . The members of the House should know. I felt we should write a bill and give it a hearing and let the House decide."

This Boland did in proposing a cutoff of the undercover aid to insurgents in Nicaragua and replacing that aid with $80 million in open funds to help Central American countries police their borders against the flow of illicit arms.

The measure was the subject of a rare secret session of the House July 19, setting the stage for the two tense and hard-fought days of public debate July 27 and 28.

"This was the first real test of whether this committee would have the confidence and respect of the House in performing its responsibility," said Boland after the vote.

His comment suggests the institutional perspective in which he and many other House members saw the issue.

In the end, presidential persuasion, nearly solid Republican ranks against the bill and hints of political danger for those who might vote to "tie the hands" of U.S.-supported fighters in Central America were unavailing against the former registrar of deeds of Hampden County, Mass., the Democratic members of his committee and their supporters in the Democratic leadership.

The strong position of Boland, O'Neill, Majority Whip James C. Wright Jr. (D-Tex.) and such Intelligence Committee Democrats as Lee H. Hamilton of Indiana, Wyche Fowler Jr. of Georgia and Dave McCurdy of Oklahoma dramatized the disaffection from the "secret war" of the strategic center of the majority party.

This is not the tocsin-sounding, hell-raising element of the House, but the core of its usually cautious Democratic establishment, which normally is willing to go along with presidents in foreign policy matters.

In the late 1960s and early 1970s, just such middle-of-the-road elements were decisive in the public and political turn against the war in Vietnam, finally making it impossible for Presidents Johnson, Nixon and Ford to proceed as they wished.

That the Democratic centrists turned publicly against "the secret war" is a message from the political system, as well as from the House establishment, that can be ignored by Reagan only at his peril in the current situation.