(Updates with real weakening, Bovespa closing)
RIO DE JANEIRO, Oct 4 (Reuters) - Brazil's currency weakened on Thursday afternoon and the Bovespa index slid on Thursday after a poll suggested leftist former mayor Fernando Haddad could inch past far-right firebrand Jair Bolsonaro in a presidential runoff later this month.
A second-round vote would be held on Oct. 28 if no candidate clinches more than 50 percent of ballots as expected in a hotly contested election on Sunday that has revealed deep divides among voters in Latin America's largest economy.
The real currency BRL= weakened 0.49 percent to 3.8824 per dollar.
Despite current volatility, a cautious optimism that the winner of Brazil's presidential elections will manage to rein in growing public debt will likely support the Brazilian real, the latest Reuters poll showed. Bovespa index .BVSP , which closed 0.38 percent down at 82,952 points, giving back some ground following a two-day rally.
A poll Wednesday night showed that in a simulated second-round vote, Haddad would get 43 percent of the vote against Bolsonaro's 41 percent, a technical tie.
Bolsonaro, a former army captain running on a law and order platform, has offended many with his racist and misogynist comments. But many business elites are betting he would promote market-friendly policies.
Meanwhile, Haddad, a Workers Party academic, is seen as more likely to overturn pro-business reforms made under unpopular center-right President Michel Temer and recently described markets as "an abstract entity that terrorizes the public."
<^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ POLL-Brazil real to rise after vote as optimism outpaces uncertainty