Their efforts were interrupted when France erupted into chaos in May 1968. Student uprisings and a general strike -- fueled in part by anger over the Vietnam War -- shut down the telephones, trains and mail. Trash piled up in the streets, while store shelves and gas stations sat empty. Mr. Romney, then a leader for the region around Bordeaux, carried empty soap containers of borrowed fuel on his moped, then drove to an American bank in Paris for food money. He saw student demonstrators turning over cars, setting fires, hurling cobblestones and battling the police.

Mr. Romney described it as "a very interesting firsthand view of a very volatile setting." But his friends say the strikes were terrifying and reinforced their respect for authority. "The social system failed. The country came to a stop," said Byron Hansen, another missionary and now a car dealer in Brigham City, Utah. "It affected me and I am sure it affected Mitt."