THE HOUSE VOTE on aid to the Nicaraguan contras is a bitter disappointment to President Reagan but not necessarily a conclusive defeat. To carry the day and just barely, the Democratic leadership had to agree to allow the House to consider an alternative range of aid proposals on April 15. The Senate will almost surely have acted by then in a manner approved by the administration. The House will have before it one or more proposals reflecting the interest of wavering Democrats in mandating a push for negotiations before military aid resumes. There may be less argument over the amount of aid and the length of the lag than over the release mechanism: should the president or Congress have the say, and exactly how.

The vote yesterday was something of an anti-climax. It provides, however, a certain interval in which Americans can think harder about the Nicaragua crisis, and not just redouble their zeal on tracks they are already on. The split in the House suggests a deep national division. But it is much more a split over means than ends. The Sandinistas have few friends in this country. The American argument is over what will best reduce their totalitarian surge, internally and in the region.

Mr. Reagan has been using a bludgeon on those with whom he has this tactical disagreement; sometimes the administration argument is put in such a way as to suggest that only its supporters take freedom to heart. This is false, and to believe it, if the president does, is to diminish the possibility of coming up with some concerted action against the Sandinistas. Some of the Democrats make the same error when, in their self-righteousness, they come to the verge of claiming that Mr. Reagan is conducting an immoral policy. On both sides a calmer tone could help build a policy consensus, which has many advantages over a policy that is enacted by a handful of votes and that leaves the losers looking for a way to reverse the outcome.

There is another crucial area in which a month's respite might be used to good advantage. Some of us think that the Latin negotiating route, which includes the use of economic, political and diplomatic pressure, offers a better answer than military action, but it is undeniable that to date diplomacy remains a paper project. It may be all very true, as Latin diplomats complain, that American detachment and disdain account for some part of the reason that "Contadora" has not moved toward real achievement. But the Contadora group, and the democracies supporting it in South America, have not been nearly energetic or purposeful enough, and they could transform the situation by doing something concrete.

What about, for openers, finishing up the Nicaraguan-Costa Rican border agreement and setting out patrols from Argentina, Brazil and Peru? Why cannot this be done in a few weeks? The Latins have an essential contribution to make, but they should not just sit around moaning about Ronald Reagan. They should make it, now.