July 27 (Reuters) - Brazilian President Luiz Inacio Lula da Silva leads Senator Flavio Bolsonaro in a simulated second-round runoff for October's presidential election, a Nexus poll commissioned by lender BTG Pactual showed on Monday.
Leftist Lula would defeat the son of former right-wing President Jair Bolsonaro in a potential runoff by 47% to 43%, according to the survey.
A July 13 poll had Lula ahead by 47% to 44%.
In a first-round scenario, Lula would lead with 42% of the votes, followed by Bolsonaro (33%), Ronaldo Caiado (6%), Renan Santos (5%), and Romeu Zema (3%).
In Brazil, if no candidate gets more than 50% of valid votes in the first round, the two frontrunners advance to a runoff.
Nexus surveyed 2,004 people July 24-26; margin of error 2 percentage points.
(Reporting by Michael Susin in Barcelona; Writing by Gabriel Araujo; Editing by Alex Richardson)