(Adds other endorsements, details on first-round results)
By Lisandra Paraguassu
SAO PAULO, Oct 5 (Reuters) - Centrist Brazilian Senator Simone Tebet, who finished third in the presidential race, on Wednesday said she was supporting leftist Luiz Inacio Lula da Silva against far-right incumbent Jair Bolsonaro when they face off in an Oct. 30 runoff vote.
The support of Tebet, who received nearly 5 million votes in Sunday's first-round vote, is a major boost for former president Lula as he and Bolsonaro seek to stitch up support ahead of a tense and increasingly competitive runoff this month.
Tebet said she would support Lula because he, in contrast to Bolsonaro, had shown commitment to Brazil's democracy and constitution. It remains to be seen how many of her voters will follow her lead in backing the former president.
On Tuesday, Lula secured the support of fourth-placed candidate, leftist Ciro Gomes, who went along with the decision of his Democratic Labor Party (PDT) to back Lula, but who did not provide the same ringing public endorsement.
Between them, Tebet and Gomes received 7% of votes on Sunday. Lula garnered 48.4% in the first round - just shy of the majority needed for an outright victory. Bolsonaro received 43.2% of votes, outperforming his polls and fanning hope among his supporters.
The president has secured the support of the governors in Brazil's three most populous states – battlegrounds in southeast Brazil where he and Lula are focusing their campaigning at the start of the second round.
Romeu Zema, the re-elected governor of Minas Gerais, Brazil's second-most populous state, endorsed Bolsonaro along with Sao Paulo's outgoing governor, Rodrigo Garcia, and Rio de Janeiro's Claudio Castro, who won his re-election bid.
The president enters the second round with wind in his sails after his surprising success in rallying conservative sentiment, which turned his Liberal Party into the largest in both chambers of Congress in Sunday's general election. (Reporting by Lisandra Paraguassu in Sao Paulo Writing by Gabriel Stargardter Editing by Brad Haynes and Matthew Lewis)