DRINKING, it's been said, intensifies the mood you're in. So may the Nicaraguan incursion across the border of Honduras intensify the American debate over aid to the contras. The incursion is reportedly the largest of scores of instances of hot pursuit of the Honduras-based contras. It is interesting that Managua made this move while Congress was in mid-passage on the contra vote. To some Americans, the incursion provides further proof of the menace the Sandinistas pose to their neighbors. To others, it exposes the risks of support for the contras. The latter point is surely the one the Sandinistas mean to impress on the Hondurans, whose unacknowledged part in an invasion of their neighbor mutes and confounds their complaints of the neighbor's invasion of them. These are dicey days in Tegucigalpa.

And in Washington. To reassure Hondurans, President Reagan immediately promised emergency military aid. But to reassure Americans he added his familiar pledge that no American troops would follow. Thus did he freshen the nagging question of why it is that a cause he insists is vitally important to the United States is, nonetheless, not worth Americans' fighting for -- not even when the contras, who are supposed to be carrying the American ball, are being tackled deep in their own backfield. The Senate is to vote on contra aid tomorrow. Until the Honduran episode at least, the debate in that chamber was proceeding on a track different from the one it took in the House. Senate Republicans were exploring ways to find "common ground," not simply to erase the defeat the administration suffered in the House but to confer on American policy the force and staying power of a bipartisan consensus. This has involved drafting two sets of incentives, one meant to encourage the Sandinistas to compromise and the other meant to encourage the administration to compromise.

The effort, however, seems to us a woeful mismatch. The Senate is miscast as a middleman between two governments, one of them its own. Pressure applied to one means the release of pressure from the other. Many people would like to have it both ways, but reality is a harsh taskmaster. In a world of imperfect choices, the question remains whether the United States is better off assuming its own strategic responsibilities in the region and, within Nicaragua proper, betting on Latin American mediation rather than on contra military action. After the raid into Honduras, as before, we would go the latter way.