The campaign to reassure the American right that there is no need to worry about Communists' taking over the Panama Canal went awry Aug. 19 when the president of Panama tried to ingratiate himself with visiting conservative Republican senators by using offensive racist and archaic American jingoistic language.

Demetrio B. Lakas, who holds the largely ceremonial role of president in Gen. Omar Torrijos's dictatorial government, referred to "niggers" and "coontown," praised the 1965 U.S. intervention in the Dominican Republic and proclaimed Uncle Sam can do no wrong. The racism left the visiting senators appalled, and the American jingoism convinced them the Panamanians were playing a con game.

Reassuring conservatives that strongman Torrijos will not join arms with Moscow and Havana is central in President Carter's campaign for ratification of the treaty transferring the canal to Panama. But the beautifully orchestrated campaign in Washington could be undercut by repetitions of President Lakas's grotesque performance in Panama.

While short on authority, Lakas is viewed by U.S. diplomats as an important adviser to his old friend Torrijos. More obviously, he is a Panamanian good ole boy useful to reassure Americans worried about Torrijos's dalliance with the Soviets. A businessman-engineer educated at Texas Wesleyan and Texas Tech, Lakas speaks English in a salty Texas accent.

So, on Aug. 19, the three conservative senators - Strom Thurmond of South Carolina, Jesse Helms of North Carolina and Orrin Hatch of Utah - were invited for coffee with the president. Lakas immediately assured them there are no Communists in Panama and "as long as we don't have them, I think we're on the right track."

He then demonstrated ignorance of how the politics of the South have changed between 1948, when Thurmond was Dixiecrat candidate forPresident and 1977, when Thurmond's 6-year-old daughter enrolls in a racially integrated school. No American politician even privately uses the language that tape recordings show Lakas using. "I was born on the other side (of the canal) in Colon, about like coontown," he said. "That's where all the niggers come from."

On a 1971 visit to the United States, Lakas told the stunned senators, "I saw a colored boy" with a white girl. "I'm from down here where we live with them, and walked with them, and played with them. And that (racially mixed couples) just doesn't look good. It's just the way you're brought up, that's all." Those sentiments coincide with private warnings by the State Department that Thurmood might well be accused of racism if he takes a "colonialist" position on Panama.

Lakas next addressed the point that may determine the treaty's fate: defense of the canal after Panama fully takes in the year 2000. It "makes me very, very happy to feel that way, that Uncle Sam will be there and be strong to be able to defend it. This is good news coming from you."

Lakas could scarcely contain his enthusiasm: "By gosh, I have never seen Uncle Sam do anything wrong." He then "off the record" talked about the U.S. 1965 intervention in the Dominican Republic to put the place "in order" because of "Communists" there.

What right was there to intervene? he asked rhetorically. "Your right is that you are right." Lakas pounded the table. "And there's nothing wrong by doing right." Lakas pounded the table again. "That's your right. You're going there to help some people; you're not going there to hurt somebody."

When Thurmond interjected that the Soviet Union is the world's greatest threat to freedom, Lakas shot back: "Sure!"

The senators left unconvinced. The table-thumping president could not blot out Panama's tightening ties with Moscow. On July 20, a broad Soviet-Panamanian commercial treaty was signed in Panama. The principal Panamanian signer, Marcelino Jaen (Torrijos's brother-in-law) issued a statement aligning Panama with the Soviet Union against unnamed "strong forces that represent a philosophy that is contrary to the destiny of Latin America." The Soviet link fits Torrijos's regional relationship with the Carribbean leftist trio of Cuba's Fidel Castro, Jamaica's Michael Manley and Guianna's Forbes Burnham.

This orientation is reason enough for studying closely the indefensible Swiss-cheese pattern of scattered U.S. military installations remaining in the Canal Zone once the treaty is ratified. The attempt by President Lakas to obscure this with good ole boy talk he learned from college days in Fort Worth and Lubbock only made the treaty's foes more wary about what lies ahead.