Brazil's 136 million voters will soon choose their next president: either Dilma Rousseff, the former right-hand woman of outgoing President Luiz Inacio Lula da Silva, or Jose Serra, an efficient ex-governor of Sao Paulo state. Serra was taking part in a rally in Campo Grande, a suburb of Rio de Janeiro, when he was struck on the head by "a heavy object" and required a medical examination. Duration: 00:49