It's too easy to put down President Reagan's "National Bipartisan Commission on Central America." Chairman Henry Kissinger is a walking controversy. The membership is only feebly bipartisan and shallow on expertise. The Reagan White House is not dumb enough to bet the president's fortunes on a runaway horse. The fix must be in.

"It's a time-buying operation," says one Senate authority, who figures for good reason that the White House wants the money right now for its military designs in Central America--that later will be time enough for a broad bipartisan policy. That, after all, is what Reagan said.

"The commission will lay the foundation for a long-term unified national approach," the president told the longshoremen last week. "Their focus will be long term," he added, as if for emphasis. "In the meantime, we cannot succeed unless the Congress approves the necessary resources."

Now that might be a manipulation worthy of a Nixon handyman. But it somehow doesn't fit Henry Kissinger, the celebrity/statesman with an eye fixed on final reckonings. Ask him, now, to head a commission in search of a policy and you can count on a "conceptual structure for peace"--global in reach, Olympian in its intellectual force, suitable for framing by historians.

That's one potential joker in the deck --one reason for not being so sure where this commission will come out. Another is that Kissinger will find himself confronting a familiar problem--on unfamiliar turf. Apart from the sorry saga of Chile, his memoirs leave Latin America to one side. His biggest dip into Central American matters, interestingly, was his sensible support of Jimmy Carter's Panama Canal Treaty, which Reagan did his engaging best to sabotage.

The familiar problem, of course, is "limited" war, for which the necessary ingredient is ample public support to demonstrate American staying power and a convincing willingness to up the ante by way of encouraging The Other Side to fold its hand. What can only make Central America more agonizingly familiar to Kissinger is that, once again, that vital ingredient is missing.

Except that, as Kissinger must surely realize, it's worse than Vietnam. Then, the problem was vibrant, vocal opposition. Now the problem much more closely resembles the "sulking isolationism" Kissinger himself predicted would be the consequence of failure in Vietnam.

Much is made of the polls showing heavy majorities against President Reagan's Central America policy. Not enough notice has been taken of the far more disturbing findings of a recent CBS/New York Times poll. Those who were found to be "informed" were, it's true, against a deepening American intervention. But the definition of "informed" was knowing "which side the United States supports in both Nicaragua and El Salvador." Some 25 percent knew the United States supported the Salvadoran government; 15 percent knew that we are against the Sandinista regime in Nicaragua.

But only an astounding 8 percent knew, in both cases, which side Ronald Reagan wants us to support. This, mind you, at a time when the White House has mounted a massive lobbying campaign with visiting special-interest groups and the president has taken to the bully pulpit of a joint session of Congress in an effort to mobilize the nation against a mortal threat to its security.

What Henry Kissinger and his crew of consensus-builders confront is not so much a public up in arms against the Great Communicator's call to the colors as a public that doesn't give a damn. Worse, those who do know what side we're on are measurably less supportive of Reagan policy than those who don't. That's something to contemplate when your mission is to seek consensus by spreading the word.

On the face of it, you could assume that Henry Kissinger would be with Ronald Reagan. He is recently on record in favor of intensified U.S. military intervention, up to and including the use of U.S. combat forces if things get out of hand. But there remains the prerequisite of public support.

And that may be the best reason for thinking it possible that, in the end, Henry Kissinger may think twice and come down most strongly on that side of Ronald Reagan's policy that the president stresses the least: the search for a global negotiated accommodation under regional rules of engagement that would not preclude the possibility that a contained Marxist-Leninist presence in the hemisphere could be made tolerable.

Kissinger stated the problem with characteristic clarity in his memoirs: "Perhaps the most difficult lesson for a national leader to learn is that with respect to the use of military force, his basic choice is to act or to refrain from acting. You will not be able to take away the moral curse of using force by employing it half-heartedly or incompetently . . . Statesmen get no prizes for failing with restraint. . . . If they are not prepared to prevail, they should not commit their nation's power."

It will be interesting to see how today's Henry Kissinger applies these principles to Ronald Reagan's practice of Central American policy.