SAO PAULO, July 15 (Reuters) - Brazilian President Luiz Inacio Lula da Silva has widened his lead over right-wing Senator Flavio Bolsonaro in the run-up to October's presidential election, a Quaest poll commissioned by brokerage Genial showed on Wednesday.
It is the first Quaest survey following a series of political developments including a corruption investigation targeting a senior Lula ally and arguments about accountability over new U.S. tariff threats against Brazil.
Leftist Lula is seen with 45% of voting intentions in a potential second-round runoff, compared with 37% for Senator Bolsonaro, currently the main opposition hopeful.
A Quaest poll in June showed Lula leading Flavio Bolsonaro by 44% to 38%.
In a first-round scenario, Lula would take 40%, Bolsonaro 28%, Ronaldo Caiado 4%, Renan Santos 3% and Romeu Zema 2%.
In Brazil, if no candidate gets more than 50% of valid votes, the two frontrunners go to a second-round vote.
Quaest surveyed 2,004 people between July 10 and 13. The poll has a margin of error of two percentage points in either direction.
Reporting by Michael Susin and Isabel Teles; Writing by Victoria Pacheco; Editing by Andrew Heavens
