By Anthony Boadle and Ricardo Brito BRASILIA (Reuters) -Brazilian President Jair Bolsonaro and his leftist challenger were hunting endorsements on Tuesday, party officials said, as they fine tuned their campaigns for a runoff in an election that has proven more competitive than expected. Former President Luiz Inacio Lula da Silva won 48.4% of the votes on Sunday, just short of the majority needed for an outright win against the far-right Bolsonaro, whose surprisingly strong showing won him 43.2% of votes. The highly polarized race, marked by threats from Bolsonaro that he might contest the res…