RIO DE JANEIRO, Oct. 15 (Xinhua) -- Brazil's right-wing presidential candidate Jair Bolsonaro slightly widened his lead in polls ahead of the Oct. 28 run-off, a polling firm said on Monday.

The Brazilian Institute of Public Opinion and Statistics (Ibope) said Bolsonaro, with 59 percent support among the electorate, has an 18-point advantage over rival Fernando Haddad who has 41 percent.

Ibope's survey queried 2,506 voters in 176 cities over the weekend, and has a two-point margin of error.

The Ibope poll appears to confirm a trend in favor of the conservative candidate, following the results of last week's survey by another pollster, Datafolha, which showed Bolsonaro had 58 percent support and Haddad had 42 percent.

Bolsonaro easily won a first-round vote on Oct. 7, garnering 46 percent of the votes in a field of 13 candidates. Haddad was the runner up with over 29 percent, according to the national electoral body.

As neither of the pair reached the 50-percent threshold to claim an outright win, a run-off has been set for Oct. 28.