By Steve Kingstone
BBC News, Sao Paulo
If population size was all that mattered, 70-year-old Claudio Hummes would be well-placed to become the next pope.
Cardinal Hummes portrays himself as a man of the future
Brazil has 125 million Catholics, more than any other nation.
His archdiocese, Sao Paulo, has a population of six million.
And Latin America is home to nearly half the world's one billion Catholics.
But Claudio Hummes offers more than mere statistics. For 30 years he has been a fierce critic of poverty and social injustice. He played a key role in Brazil's return to democracy in the 1980s. And crucially, he was close to John Paul II.
In March 2005 he told a Vatican conference that "solidarity with the poor" was indispensable for long-term world peace. He asked: "Does not today's terrorism have as one of its ingredients a revolt against an imposed poverty?"
Friend of unions
Born in 1934, the son of German immigrants, Claudio Hummes was one of 15 children. He became a priest in 1958, joining the Franciscan order.
After studying philosophy in Rome and ecumenicalism in Switzerland, he returned to Brazil. In 1975 he became Bishop of Santo Andre, an industrial suburb of Sao Paulo.
At the time, the country was under military rule, and Santo Andre was the emerging power base of the trade union movement.
President Lula (left), once a union leader, sees Hummes as a friend
"The military would quickly shut down any union meeting," says Anna Flora Anderson, a lecturer at the Dominican School of Theology in Sao Paulo. "So one of the great things Claudio did was to open up the smaller churches - so the unions could meet without interference."
Democracy was restored in Brazil in 1985. And many of today's political leaders are indebted to Claudio Hummes for the protection he offered.
"He's a good friend," says President Luiz Inacio Lula da Silva, a former leader of the metalworkers' union in Sao Paulo. "And I would love a Brazilian to be the next pope."
Bishop Hummes became Archbishop in 1996 - first in the north-eastern city of Fortaleza, and then in Sao Paulo (1998). He was elevated to cardinal by John Paul II in 2001.
Throughout his rise, his sense of social justice was balanced by a strict moral conservatism. He strongly opposes abortion and gay marriage.
He says the use of condoms violates Catholic values - with their emphasis on the sanctity of human life. And adds: "It's for the manufacturers of condoms to say whether they offer protection against the risk of HIV."
"The previous Archbishop of Sao Paulo used to call condoms a necessary evil," says Jose-Carlos Veloso, of the Support Group for the Prevention of Aids. "But Hummes doesn't go that far. He positions himself as the Vatican's direct representative in Brazil."
Cardinal Hummes has often stressed his close affinity with John Paul II, whom he has described as "a father figure" and a "great mentor".
But he also portrays himself as a man looking to the future. In interviews, he raises modern themes such as biotechnology and stem cell research.
"The world has made rapid progress," he says, "but some feel that the ethical dimension is being neglected. The Church must join the dialogue, and find answers to these big new questions."
Detractors of Cardinal Hummes accuse him of being a chameleon - a man who shifts the emphasis of his faith depending on his audience. But supporters praise his inclusiveness, and the fact that he refuses to be labelled.
"He could be a very good pope," says Cardinal Paulo Evaristo Arns, who was his predecessor as Archbishop of Sao Paulo.
"He's very intelligent, steadfast and sincere. And crucially, no-one can really define him. On some issues he's conservative and on others liberal."