Talk about bootless acrimony! Whatever the final outcome, the debate on Nicaragua has told us more about the rancorous way we go about making difficult foreign policy decisions than it has told us about the heart of the matter: the probable consequences of this or that course of action and the prospects for accomplishing purposes within our reach.

First, my own sense of it: even the full $70 million in new military aid and $30 million in "humanitarian" aid that Ronald Reagan wants for the Nicaraguan contras would not be enough to accomplish the president's thinly concealed design. You have to believe that he wants to transform (let's not quibble over words like "overthrow") a Sandinista regime which is not going to negotiate itself out of power and can only be replaced by force.

Even the president seems to agree on that. He is already talking about more aid -- after the $100 million. He is talking about U.S. military advisers in contra camps in Honduras. He is talking, then, about a deepening, incremental, open-ended commitment. No such commitment can, in all logic, preclude the ultimate need for American forces, if the effort remains inconclusive and the stakes are anywhere near as apocalyptic as the president would have us believe. So the opposition has a right to make that point, and the president would be on stronger ground if he conceded it.

For his part, Reagan has every right to argue, out of deep conviction, that abandonment of the contras means an unacceptable threat to neighboring "fragile" democracies -- and our own security. His critics, accordingly, are obliged to be more forthcoming about their willingness to accept that risk.

The president, in turn, owes the opposition a better answer to its argument that to remove a conspicuous U.S. military hand in Nicaragua might free other, more effective, hands: Latin Americans who outwardly oppose U.S. policy but are fearful of the Sandinistas, opponents argue, could be in a stronger political position to exert diplomatic efforts to contain the external Nicaraguan threat. That's what the debate comes down to -- a careful balancing of choices and necessarily speculative consequences.

Now and again you get glimpses of such a debate. But more often, it is lost in hype and hyperbole, in slanging matches that have more to do with ideological passions or the onset of congressional elections than with any serious effort to work out differences.

The president pleads for bipartisanship, citing the immediate postwar years of the Atlantic Alliance, the Truman Doctrine, the Marshall Plan. But he cannot have the slightest sense of how bipartisanship worked.

On the rare occasions when it did work, the director of communications in the White House was not reaching out to touch the opposition with the nasty smear that they had become "with Moscow, co-guarantor of the Brezhnev Doctrine in Central America." The State Department's man in charge of hemispheric affairs was not saying on television that all the critics really wanted to do was to "knock Ronald Reagan in the chops."

Bipartisanship imposes upon its serious practitioners a certain civility, if not sweet reason. That's not to exonerate the Democrats. Their charges of "McCarthyism" should be reserved for ugliness of a higher order.

A serious decision, then, is being dealt with in sometimes disingenuous and, often careless, ways. The administration has rewritten the history of the contras, grotesquely recasting the whole movement (a motley crew which does include some worthy elements) in the image of our Founding Fathers.

The makers of the Marshall Plan, by contrast, relied on the careful findings of bipartisan study committees headed by the likes of Henry Stimson, Averell Harriman, Christian Herter. If this is as big a deal as the president insists, it cries out for as honest an effort to mobilize the widest public support.

Instead, positions are being taken in a congressional year, and in an artificially pumped-up atmosphere of near hysteria over the security of Harlingen, Texas. Whatever the ultimate decision on support of the contras, it will have been flawed seriously by the manner in which it is being made. That can only introduce commitments, one way or the other, that will confound sound judgments in some future, less fevered time.