SAO PAULO, Oct 3 (Reuters) - Brazilian President Luiz Inacio Lula da Silva's lead over Senator Flavio Bolsonaro narrowed ahead of Sunday's first-round vote, a CNT/MDA poll showed on Saturday, while also pointing to a tighter race in a likely runoff.
In a first-round scenario, Lula would receive 43.1% of voter support, followed by Bolsonaro (38%), Augusto Cury (3.2%), Ronaldo Caiado (3%) and Renan Santos (1.5%), according to the poll.
A September 15 poll had Lula at 40.5%, Bolsonaro at 30.4%, Cury at 6%, Caiado at 3% and Santos at 2.7%
Considering only projected valid votes, which exclude people telling the pollster they would leave their ballots blank or void somehow, Lula reached 47.8% voter support against Bolsonaro's 42.1%
If no candidate wins more than 50% of valid votes in the Sunday first round, the two frontrunners advance to a runoff on October 25
In a likely runoff, Lula would receive 47.3% of voter support, compared with 43.1% for the eldest son of former President Jair Bolsonaro, the poll said
In the previous survey, Lula led Senator Bolsonaro by 47.3% to 40% in the runoff
MDA surveyed 2,007 people from September 30 to October 2, with a margin of error of 2.2 percentage points
(Reporting by Eduardo Simoes and Gabriel Araujo; Editing by Alison Williams)