Now, holding the lead a week ahead of the presidential election, he's threatening to be ''a nightmare for the government of the United States.''

It's not hard to see why. The 46-year-old candidate is a staunch leftist who counts Cuba's Fidel Castro and Venezuela's Hugo Chavez among his close friends. Moreover, he's a coca farmer, promising to reverse the U.S.-backed campaign to stamp out production of the leaf that is used to make cocaine.

With his Aymara Indian blood and a hatred for the free-market doctrines known to Latin Americans as neo-liberalism, Morales in power would not only shake up Bolivia's political elite, but strengthen the leftward tide rippling across South America.

''Something historic is happening in Bolivia,'' Morales told The Associated Press in an interview. ''The most scorned, hated, humiliated sector now has the capacity to organize.''

At a recent campaign stop in the western highland town of Caracollo, Morales and members of his Movement Toward Socialism party were mobbed by crowds who kissed them, showered them with confetti and draped necklaces of flowers and fruit around their necks.

''I have no fear in saying - and saying loudly - that we're not just anti-neo-liberal, we're anti-imperialist in our blood,'' he told the rally.

Morales, who has already been involved in toppling two presidents, has come close to winning the presidency once before, and is now running strong against conservative former President Jorge Quiroga and several other candidates. If no one wins an outright majority next Sunday, Congress will choose between the top two vote-getters.

The latest poll by Ipsos-Captura shows Morales with 32.8 percent, five percentage points above Quiroga, and gives a margin of error of two percentage points.

''Symbolically, he would represent a fundamental change,'' said Jimena Costa, a political science professor at Bolivia's Universidad Mayor de San Andres. ''It's not just the first time an Indian would win the presidential elections, but he would be doing it with the support of a sector of the white and mestizo community and urban populations.''

While the U.S. government insists that much of the Chapare's coca becomes cocaine, farmers say they supply a legal market. Coca leaves are sold in supermarkets and can be chewed, brewed for tea, and used in religious ceremonies.

''I hope there aren't changes, because if there are changes for the worse, the country that's going to suffer is Bolivia,'' Greenlee told an anti-drug rally in El Alto, a slum city next to La Paz.

Morales still maintains coca fields and pledges an international campaign to legalize the leaf and industrialize its production. He insists he will fight drug trafficking, but maintains that the plant has been wrongly maligned.

The free market policies that have failed to pull Bolivians out of poverty have empowered the country's poor Indians to demand change. Morales became an important figure in waves of protest that brought down Sanchez de Lozada in 2003 and his successor, Carlos Mesa, in June.