"This will be our task, we Republicans, to reconstruct a vast bipartisan consensus and to follow a foreign policy which appeals to the most qualified elements and the most pertinent opinions on foreign policy and on national security issues."

That's Richard Allen speaking in an interview in a French periodical, Politique Internationale, last fall, when he was candidate Ronald Reagan's principal foreign policy adviser.

"I don't think we can have for long a foreign policy which is either Democratic or Republican," he went on. "This is how a Reagan administration would conceive of its mission and its responsibilites."

Well, there's nothing wrong with thinking big. And there also is no reason to question the sincerity of Allen, who is now President Reagan's national security adviser, or the Secretary of State Alexander Haig when both men speak earnestly of the need for an American foreign policy with broad, bipartisan support.

"Our urgent task is to reestablish an effective policy consensus," Haig told the Senate Foreign Relations Committee in the hearings on his confirmation. "Congress can hardly be expected to allow the president the discretion he requires unless it is comfortable with the purposes toward which, and the limits within which, that discretion will be excercised." t

Fair enough, but first things first. Before the administration can hope to make Congress "comfortable" or achieve a "vast bipartisan concensus," it must forge a consensus in its own house on what the president's policy ought to be. And already there are the first faint signs that the Reagan foreign policy making machinery may not be as smooth-running and friction-free as advertised.

At first blush, the president's foreign policy management reforms look promising. Allen himself, as one committee member noted wryly at the Haig hearings, has pledged publicly more than once on national television that he won't be speaking publicly on national television in his new job. The first recruits to his national security staff have been firmly instructed to be quiet, and invisible.

The White House table of organization doesn't even show a direct line from Allen to the president. The line of authority has him reporting to the White House counselor, Ed Meese, who, despite the absence of any known experience in international affairs, will be in overall charge of foreign as well as domestic policy.

There will be, in short, no Zbigniew Brzezinski.

We have Haig's word for it that Reagan wants him "to serve as the general manager of American diplomacy . . . with clear responsibility for formulating and conducting foreign policy, and for explaining it to the Congress, the public and the world at large.

"The assistant to the president for national security would fill a staff role for the president."

That's one way of putting it. But Allen's Politique International interview puts it a little differently: "The secretary of state, responsible for the day-to-day conduct of foreign affairs, will be the principal spokesman for the president -- which does not mean the president will not have other advisers . . . I would say that the national security adviser will be a sort of mediator harmonizing the interests of different groups dealing with foreign affairs."

A mediator's role, of course, can be critical in the shaping of policy. It would be unlikely, in practice, to keep Allen at one remove from the president. "That chain of command will break down quickly," says one of the new White House appointees, who reckons Meese will need to depend heavily on the expertise of Allen and his staff. "I doubt if the president will talk foreign policy with Meese without Allen in the room."

This arrangement doesn't automatically mean conflict between the White House and State. Haig and Allen are thought to see eye to eye on most foreign policy issues.

But already there are angry rumblings from the far right over Haig's sub-Cabinet choices at State. Sen. Jesse Helms (R-N.C.) and as many as a dozen other hard-core Reagan supporters reportedly have filed a vigorous protest. Hais is said to be hanging tough. But the struggle for consensus on a Reagan foreign policy (let alone a bipartisan one) has only just begun.

In that struggle, Al Haig may have the leading role. But the White House combination of Meese, Allen & Co. figures to be a potent force.