CURITIBA, Brazil (Reuters) - The national executive of Brazil's Workers Party decided on Tuesday that Fernando Haddad will be its presidential candidate, replacing the party's jailed founder, former president Luiz Inacio Lula da Silva, a party source told Reuters.

The official asked not to be named because the decision has not yet been made public to replace Lula, who has been barred from running due to a corruption conviction. Support for Haddad, a former Sao Paulo mayor, surged in a poll done on Monday that showed him tied in third place for the Oct. 7 vote.

(Reporting by Lisandra Paraguassú; Editing by James Dalgleish)