CONGRESS should vote enough aid to keep the contras going for now. To squeeze out the contras at this point, while they are still a presence affecting the bargaining, would be self-defeating. This requires a little give on all sides. When Nicaraguans of opposing persuasions are being called upon to make huge concessions, it is self-indulgent for Americans not to make small ones. We have especially in mind House Democrats who want to burden the token bridge aid now under discussion with arbitrary restrictions on its use. This is unhelpful posturing. The Reagan administration is flexible by comparison.

Events are building toward a political climax of sorts in January, when the leaders of Central America are to decide whether the peace plan is working and should be sustained or whether it is failing and must be abandoned. Few people expect the latter verdict. Not only are the implications, of deepening and spreading war, too frightful for most Latins to contemplate. The actual state of observance is going to be mixed. The choice in January is not going to be a stark up or down. The question will be whether to keep up energy toward a settlement or to relapse into a condition of sloth on some fronts and confrontation on others.

To play its part in preventing the Arias plan from becoming ''another Contadora'' -- a time-wasting substitute for responsible collective action -- the United States has some clear duties.

It should keep applying the pressure -- as much symbolic as real -- of bridge aid to carry the contras into the Latins' January stock-taking.

It should press full steam ahead to explore Mikhail Gorbachev's hint of an end to military aid to the Sandinistas; evidently this would be linked to defunding the contras and movement on peace. That the Sandinistas -- nervous about Soviet intentions? -- speak of a great increase of aid only underlines the requirement to consult. Such a buildup is utterly incompatible with the improvement of Soviet-American relations Mr. Gorbachev describes as his goal.

Finally, the United States has to do what it can most usefully do to hold the Sandinistas to their pledges of a political opening. The American political system is in fact doing this in its rough fashion: keeping open the twin possibilities of toughness if Managua cheats and cooperation if Managua plays fair.