THE OTHER DAY Nicaragua sent troops to hit contras in Honduras. It was a border-crossing operation of a sort that has become routine since Honduras started providing the contras bases in 1982 -- so routine that the president of Honduras did not see fit to interrupt his Easter week holiday. Things were a bit different this time, however. The operation seems to have been larger than usual. And the Reagan administration seized on it as ammunition for its aid campaign in Congress, claiming it proved the Marxists in Managua are on the march.

It proved nothing, of course, that was not already evident in the conduct of the Nicaraguan war. The Reagan administration acts as though the government in Managua, which it recognizes, should stand still and not retaliate against American-supported insurgents trying to overthrow it. American protestations of an "invasion" skip slyly past the fact that Honduras has been the contras' launching pad for years. Some large part of whatever threat the Sandinistas may pose to Honduras arises directly from Honduras' contra connection.

At least as off the point has been the response of the House Democratic leadership. Speaker O'Neill called the Sandinista incursion a "tremendous blunder," meaning, we suppose, that it embarrassed Speaker O'Neill, who opposes contra aid. But the reason to oppose contra aid has never been that the Sandinistas are okay guys who unfortunately are prone to political blunders at aid-voting time. It is that the Sandinistas are nasty guys who, in the hard existing circumstances, can be better contained by Latin political envelopment than by any feasible military assault by the contras.

The Reagan administration, in any event, was able to make political use of the trouble in Honduras. Whether its hyping helped or hurt or made any difference is not clear, but the administration did win the Republican-controlled Senate's approval last night for the contra aid plan that the administration had failed to sell to the Democratic- controlled House last week. The House is to take up the issue again after Easter. By then, hostile forces may have crossed the Nicaraguan-Honduran border again, from both sides.

If the United States is in fact troubled by Nicaragua's border transgressions, then its smartest choice is to support the latest Nicaraguan call for the border to be sealed and patrolled by the Contadora countries. Otherwise the administration leaves itself in the untenable position of demanding that the border be closed in one direction only.

We mixed up a "former" with a "latter" in our editorial "Add Honduras" on Wednesday, with the effect of seeming to endorse the pro-contra aid position. We don't: it was a linguistic slip, not a political change of heart. As between Latin American mediation and contra military action in Nicaragua, we continue to favor the former.