By Ricardo Brito
BRASILIA, July 31 (Reuters) - Brazil's Progressives Party, one of the country's largest right-wing parties, said on Friday it would stay neutral in October's presidential election, a significant setback for Senator Flavio Bolsonaro, the strongest conservative contender in the polls, after he tried tapping one of its members as his running mate.
If upheld, the decision would close the door on Senator Tereza Cristina joining Bolsonaro's ticket as running mate, despite his announcement to reporters earlier on Friday that he had chosen her for the role.
Cristina enjoys strong backing among rural voters and the powerful agribusiness caucus, which would be a major boost for Bolsonaro to win over voters as he trails President Luiz Inacio Lula da Silva in polls ahead of the October vote.
• Senator Bolsonaro, the eldest son of former President Jair Bolsonaro, seeks to broaden support for his campaign and add a woman to the slate.
• For her to become Bolsonaro's running mate, her party would need to formally align with Bolsonaro's Liberal Party (PL).
• The deadline for changing parties ahead of the October election has passed.
• Earlier on Friday, Bolsonaro told reporters in São Paulo that Tereza Cristina had accepted his invitation to join his ticket.
(Reporting by Ricardo Brito, writing by Gabriel Araujo and Isabel Teles, editing by Manuela Andreoni and Susan Fenton)
