Things were bleak enough for President Reagan on the contra front when Oslo had to get into the act and make them worse.

Reagan said a terse, "I congratulate him," when reporters shouted to him for reaction to the bad news.

The award produced something of a crisis at the State Department. Elliott Abrams, assistant secretary for inter-American affairs, who regards the Arias peace plan as poison, was late arriving to open a day-long seance on Nicaragua being sponsored by the State Department and featuring such luminaries as Arturo Cruz Jr., a confederate of Oliver L. North. Cruz senior quit the contras because he couldn't stand the leadership.

Abrams was closeted with Secretary of State George P. Shultz. They were drafting a statement of congratulation that they hoped would not reflect too vividly the consternation they both felt at the world recognition of the peace-making president of Costa Rica, Oscar Arias.

Later, Shultz, appearing before the House Foreign Affairs Committee, had to undergo a lecture from Rep. Mel Levine (D-Calif.), who said he found it "sad and ironic" that Shultz was asking for $270 million in aid to the contras on the day that Arias was being honored with the highest prize that any politician can aspire to. Arias, Levine pointed out, devised his peace plan on the theory that the real obstacle to peace in Central America was the U.S.-backed contra force.

Shultz had no comment.

Jubilant Democrats think the war over the contras is over. They are not surprised that Reagan, for whom peace means a bitter personal defeat at the hands of the Sandinistas, has failed to seize the opportunity to throw his arms around Arias and claim that they had done it together. As the failed Bork nomination proves, Reagan doesn't know when to quit any more.

They anticipate that the president, and Republicans in the coming presidential campaign, will insist that Nicaragua makes democratic concessions only at gunpoint. They think he could try to vindicate himself there, as in arms-control negotiations with the Soviets, by a show of force and toughness.

But Democrats say that they can handle giving him credit, that the important thing is what he does when he gets to the table.

Besides, they insist, Arias, who represents an impeccable democracy so peace-loving it does not maintain an army, changed the whole Central American equation. He brought about a local settlement in the course of one short week. Arias called Nicaragua's bluff. Daniel Ortega has insisted for the last five years that the only reason the promises of the revolution were not redeemed was because of the murderous, draining presence of the contras.

Arias took him at his word. Reagan thinks this is a mad and reckless course. But Latin Americans, their pride in a solution of their own increased by the Nobel Prize for the author, are acting as if peace had already broken out.

In El Salvador, some 4,500 refugees have returned from exile in Honduras and are resettling in their home province. Their "Going Home" project is being sponsored by the U.S. religious and peace groups that have resisted the contras from the beginning. President Jose Napoleon Duarte is opposing the return because the refugees were quartered in camps frequented by rebels. But resettlement is one of the promises of the peace plan, and Latins seem to think it is in operation.

Administration hopes that Ortega would defy his neighbors and sabotage the agreement died early. Ortega played his trump immediately -- he reopened La Prensa. He held that card for four years while delegations of anti-contra U.S. lawmakers grew hoarse pleading with him to play it.

Sen. Terry Sanford (D-N.C.) is working on a next step, an ambitious economic-recovery plan for Central America. A commission and a task force in place at Duke University, of which he was recently president, will analyze the crushing economic problems of the region and offer assistance, most of it privately financed, to nations abiding by the provisions of the Arias peace plan.

The commission will set up shop in San Jose, Costa Rica. Its U.S. membership includes Arthur Levitt Jr., chairman of the American Stock Exchange, lawyer and ex-diplomat Sol Linowitz and representatives of unions and universities. The preparation will take 18 months. The plan will be ready for the new president.

Elliott Abrams warns that "no communist country has ever turned democratic." But nobody is listening. Everybody wants to see if Nicaragua could prove an exception. Arias, with a huge assist from House Speaker Jim Wright (D-Tex.), has made it possible to find out.