By Paulo Prada RIO DE JANEIRO (Reuters) - Criminal charges and a request by prosecutors to jail Luiz Inácio Lula da Silva are putting the former Brazilian president and leftist icon back in a role he has long relished: that of the martyr. Last week, after federal police took him into custody briefly for questions about a far-reaching graft probe around Brazil's state-run oil company, Lula said he "felt like a prisoner" and urged leftist organizations, from landless peasants to labor unions, to rally. "I am going to travel this country." For the beleaguered government of President Dilma Rousseff, Lula's successor and protégée, any traction Lula gets could provide relief at a time when it is crippled by impeachment proceedings, an economy that shrunk by 3.8 percent last year and a corruption scandal that is drawing ever closer to her inner circle.