At 1:30 p.m. Tuesday, a Republican congressman slipped Adolfo Calero a draft document that threatened his contras with the grim fate so often faced by anticommunist fighters who put their faith in the United States.

Only two hours earlier, the civilian leader of the Nicaraguan resistance had been tipped on the August ''peace'' plan unfolding behind his back. Unable to believe Ronald Reagan would so mistreat the contras, Calero told a friend he wanted to hear it from the president's own lips. Instead, his 11 a.m. Wednesday appointment was postponed one hour, letting Reagan duck him until the plan was announced.

The ''peace'' shock was equally unpleasant for contra backers in Congress and the administration. Thought up and drafted by Speaker Jim Wright, it was rushed out in 10 days by presidential aides with help from the National Security Council staff and the State Department. But no NSC meeting was held, and no chance was afforded congressional leaders to remonstrate with the president.

The process started when Wright met with Carlos Tunnermann, Nicaraguan ambassador to Washington. According to Wright's account to the administration, he told the Sandinista envoy not to be so sure contra aid would not be renewed. The speaker, eager to be a constructive foreign-policy maker in contrast to predecessor Tip O'Neill, began drafting a ''peace'' plan.

The speaker's followers were not happy -- particularly House Majority Leader Thomas Foley, an erstwhile centrist turned fervent foe of the contras, and chief deputy whip David Bonior, a leading Sandinista apologist. But Wright found a kindred spirit in a fellow Texan: ex-representative Tommy Loeffler, badly defeated last year for the Republican nomination for governor and brought back to lobby Congress for contra aid.

Loeffler, a former chief deputy whip, took a static head count showing not enough House votes to renew aid. That took into consideration neither Oliver North's pro-contra stir nor the impact had the president canceled his California vacation to campaign for aid. Along with House Minority Leader Robert Michel, Loeffler and Wright gave birth to the ''peace'' plan. White House chief of staff Howard Baker played eager midwife.

Barring even U.S. military maneuvers in Honduras and not providing for 17,000 contras now inside Nicaragua, the document was closely held. When he saw it Monday, Defense Secretary Caspar Weinberger protested -- to no avail. GOP leaders, first alerted Monday, were not happy. But when Loeffler said ''the president really wants it,'' they acquiesced.

Calero and the new contra directorate, knowing nothing and delighted in success against the Sandinistas (17 helicopter gunships downed this year), arrived to meet Reagan. Conferring with Secretary of State George Shultz Tuesday, Calero heard not a word of what was coming. Sadder and wiser after being slipped the draft document, he talked to conservative Republican senators Tuesday afternoon about how to unlock a presidential decision. No way. Senate Minority Leader Robert J. Dole set the tone by endorsing the plan with a highly skeptical statement.

But Rep. Jack Kemp, Dole's presidential rival, burned his bridges. Having resigned from the House GOP leadership when he announced his candidacy, Kemp was unable to see the president or get calls to Baker returned. At the House GOP conference Wednesday, Kemp denounced the plan's implicit ''moral equivalency'' between democracy and communism. Rep. Danny Burton agreed, warning that the Vietnam Paris peace talks and Korean Pammunjom negotiations were being replayed.

Privately, the White House claims Ortega either will not sign the agreement or not comply with it if he does (since Soviet MiGs are in the Sandinista supply line and the new airfield at Huete is almost ready for them). If so, there is no pledge for the speaker to vote for contra aid himself or lead his party there.

Protracted cease-fire is the probable outcome, with talks extending well beyond Sept. 1. That would debilitate the contras and confirm Sandinista rule. As so many anticommunist leaders before them have done, Calero and his colleagues left Washington weighing the rewards and costs of Uncle Sam's friendship.