BRASILIA, Sept. 12 (Xinhua) -- Brazil's presidential race has moved into high gear as candidates jockeyed for position after popular former President Luiz Inacio Lula da Silva was recently disqualified from running.

A runoff is likely to be held as no candidates have a clear lead in the first electoral round. Lula's left-leaning Workers' Party (PT) has named a substitute candidate and it remains to be seen how much of the support for Lula will migrate to the new candidate.

Lula's candidacy had been disqualified in late August due to his conviction and imprisonment on corruption charges. Polls in the runup to the Oct. 7 general election show the former president had led the field of hopefuls with a comfortable margin of nearly 40 percent.

Lula's popularity had kept him in the race even while he was behind bars, with some hoping that he would be able to win an appeal to stay in the race.

The definitive ruling against him finally came on Tuesday after the uncertainty swirling around his candidacy lingered for months.

Brazil's top election body had set a deadline for the PT to name a substitute candidate. The party finally nominated former Sao Paulo mayor Fernando Haddad.

It remains to be seen how many of Lula's followers Haddad will be able to win over, or whether some of that support will migrate to the candidates of rival parties.

"Our name is now Haddad," Lula wrote in a message read to supporters late Tuesday at a rally presenting his replacement.

With Lula out of the race, the candidate with the most backing is extreme right-wing Jair Bolsonaro of the Social Liberal Party (PSL). He has the support of 26 percent of the registered voters, according to the latest poll by the Brazilian Institute of Public Opinion and Statistics (Ibope).

Other candidates include former Ceara state governor Ciro Gomes, former Environment Minister Marina Silva, former Sao Paulo governor Geraldo Alckmin, and Haddad. They each have support of 8 percent to 11 percent.

Bolsonaro, an outspoken conservative who has publicly praised the days of Brazil's military regime, seems to have some sympathy support after he was stabbed in the abdomen at a campaign event last week.

Alckmin, another conservative, is the main rival of Bolsonaro, but polls show his candidacy has failed to take off.

On the left end of the political spectrum, voters have Haddad, and Gomes, an experienced politician who seems to be gaining ground.

No candidate is expected to win the first electoral round in October.

"The runoff will be between a red (leftist candidate) and a blue (conservative candidate). The red should be Haddad, who will shortly have the votes of more than 50 percent of voters in the (poorer) northeast," political analyst Alberto Carlos Almeida told Xinhua.

"The blue has yet to be decided between Alckmin and Bolsonaro," said Almeida, who has written books on Brazilian elections.

"If Alckmin doesn't start to take votes away from Bolsonaro in favor of the PSDB (Brazilian Social Democrat Party), he will run the real risk of not passing to the runoff," said Almeida.

A new poll is expected on Friday, which may shed more light on the trends. In the meantime, "Haddad will continue to rise," he said.

Both Haddad and Gomes rose in the results of a latest survey by polling firm Datafolha, released on Monday.

Some 47 percent of the voters in Brazil's northeast don't know Haddad, but the region is a PT stronghold.

Silva, of the Brazilian Sustainability Network (REDE), has moved to distance herself from the PT by criticizing Lula, suggesting she may plan to court the more conservative votes.

The uncertainty around the presidential election has affected the financial market, with the Sao Paulo Stock Exchange taking a hit and the national currency sliding against the U.S. dollar recently.

"Investors are going to be observing the performance of Ciro Gomes and Fernando Haddad in an attempt to gauge their chances in a runoff against Bolsonaro," investment consulting firm Commcor said in a report on Tuesday.

They should also keep an eye on Alckmin, though "he remains weak," the report said.