Michael V. Townley, now accused of having arranged the 1976 assassination of Chilean exile leader Orlando Letelier, might still be an unassuming automobile mechanic in Miami had his wife not insisted that they return to Santiago in late 1970, shortly after Salvador Allende's election as president of Chile.

"I was the one who insisted that we return," Chilean-born Mariana Callejas de Townley said this week as she sketched the life she and her American husband - being held without bail in the United States on a murder charge - have led since their marriage 18 years ago.

Callejas freely acknowledges that it was her devotion to political causes - ranging from Israel, where she worked on a kibbutz as a teenager, to Eugene McCarthy's anti-war crusade in 1968 and eventually to the overthrow of Allende's leftist government in 1973 - that finally drew her husband to an anti-Allende rally six years ago, where his right-wing, anti-Communist views suddenly formed.

Callejas has been the source of much of what is know about Townley. Much of her information - but not all - has been accurate.

In her view, everthing that Townley has done in the past several years, including his alleged involvement in Letelier's murder, stems from an 1972 incident at an anti-Allende rally.

While attending the rally the couple saw three policemen attack an old man. The old man fell to the ground, she said, and they helped him up. The incident, she added, was the moment when her husband decided " we had to do something."

Before the 1973 coup, Callejas said, Townley set up a clandestine radio station in a little car they owned, broadcasting anti-Allende messages as they drove around Santiago.

Later, he carried out a clandestine mission for anti-Allende forces in concepcion, a city south of Santiago, where jamming devices had been installed to interfere with an illegal television station set up by the rightists.As the rightist group worked to destroy the famming apparatus, a night watchman was killed, and although Callejas says her husband had nothing to do with the man's death, Townley was forced to flee to Argentina until after the military overthrew Allende in September 1973.

Townley, according to the picture drawn by his wife, was never a good student, finally getting a high school diploma through a correspondence course while living with his parents in Chile. Townley's father was head of Ford Motor Co. here during the late 1950s.

But Townley did have talents that were helpful to Allende's opponents, once he dicided to join with them, and later extraordinarily useful to Chile's secret police force, the old Directorate of National Intelligence (DINA), for whom he was working, according to Callejas, when Letelier was assassinated in 1976.

For about a year after he returned from Argentina to Santiago, Townley had nothing more to do with Chilean politics, according to his wife. He went back to his job fixing automatic transmissions and the Townleys enjoyed a varied social life, including, she said, parties at the home of Frederick Purdy, then the U.S. consul in Santiago, who gained a certain notoriety as a result of charges that the consulate failed to help a young American filmmaker who was picked up shortly after the 1973 coup and murdered allegedly by Chilean police.

Callejas claimed not to know whether her husband was involved in taking Letelier's life. But, she added, - referring to the charge, against him in the Unted States - I do not expect my husband to walk out free."