Brazilian markets got bullish on the recent surge of a candidate who could knock Dilma Rousseff out of the presidency—but that doesn't mean all of the country's business interests share the enthusiasm.
Marina Silva, an environmentalist, has emerged as President Rousseff's biggest threat in the Oct. 5 election, after Brazilian Socialist Party presidential candidate Eduardo Campos was killed in a plane crash two weeks ago. The 56-year-old Silva was running with Campos as vice president, but has since become the party's presidential candidate.
A recent poll shows Silva in second place with 21 percent support, 1 point ahead of market favorite Aécio Neves of the Brazilian Social Democracy Party—and still 15 percentage points below Rousseff of the Worker's Party.
However, in a likely second round, Silva would get 47 percent while Rousseff would get 43 percent, the poll indicated. That's a technical tie, considering the poll's 2 point margin of error.
"The degree of discontent with the current administration is very high within financial markets, and even within the business sector," said Chris Garman, head of emerging markets research at Eurasia Group. "Market participants are looking for an administration that can bring back more responsible economic management. That's what's driving asset prices."
Brazil's teetering economy, the world's seventh largest, has seen business and consumer confidence fade this year. Its inflation stands at around 6.5 percent, and the central bank cut its 2014 growth forecast to 0.79 percent this year, below the previous, 0.81 percent forecast. And now, Brazil's labor force is showing signs of struggling.
Read MoreCNBC Explains: What is a 'BRIC'?
Investors are optimistic about Silva because "it reduces the chances of Dilma winning, and I think that in any case it's a positive market event," Ilan Solot, emerging markets currency strategist at Brown Brothers Harriman, told CNBC.
Some analysts point out that the poll results could be a temporary, emotionally charged blip—the sudden death of Silva's running mate shocked the country.
"The support may depend on whether the family of Campos assumes a more proactive stance in supporting Mrs. Silva as the inheritor of Campo's legacy," Barclays said in a recent note, adding that Campos' brother has already expressed his support for Silva.
Others believe she may still pull more voters on her side, as she did in 2010, when she ran for president under the Green Party and gained almost 20 percent of the vote, far more than expected. Silva's personal history resonates with regular Brazilians: She was born to a poor family of rubber tappers—workers who extract latex from rubber trees. She once worked as a maid and struggled to obtain her college education.
"She is too radical when it comes to environmental rules. She can propose or forbid ways of work for the agriculture business in Brazil."
There's also the question of whether Silva could bring about the economic change investors want if voter support for Silva is real and she becomes president. It may be too soon to know the answer, but there are a couple of things on her side.
Analysts such as Bruno Rovai at Barclay's point to Eduardo Giannetti da Fonseca, an economist and top adviser to Silva, who has a similar economic program as that of market favorite Neves. It includes reaching an inflation target, controlling expenditures, increasing surplus and allowing a free-floating exchange rate.
"All of these measures that not only Marina (Silva) has stated but also her economic adviser has stated, they all account for higher odds of a change in the macroeconomic management," Rovai said. "It would be positive for the business sentiment, the consumer sentiment, and this would eventually lead to higher investment, higher consumption and then a recovery of the activity growth in the medium term."
However, Silva's strong environmental roots make investors and the agriculture business nervous.
As a senator and as the environment minister under President Luiz Inácio Lula da Silva, Rousseff's predecessor, Marina Silva fought for environmental protection policies to reduce deforestation. She also opposed approval of hydroelectric dams on the Amazon and was against the planting of genetically modified crops. Under Silva's efforts, deforestation dropped by almost 60 percent, according to reports.
"She is too radical when it comes to environmental rules. She can propose or forbid ways of work for the agriculture business in Brazil," said Juliana Kampf, who manages business for her father, a crop duster in southern Brazil. "We are a producer country, and if we have restrictive environmental laws, we cannot produce anymore. Things could get harder and harder for producers."
Silva's views have turned some in agribusiness against her, but that's where her vice presidential candidate, Beto Albuquerque, could come to the rescue. He is from the southern state Rio Grande do Sul, an important agricultural region.
Albuquerque "would likely boost support for Marina Silva in the South and Southwest states where agribusiness is strong and where the rejection rate polled by Ms. Silva is the highest," Goldman Sachs said in a recent note.
Other key things experts say are watching for as Silva's campaign evolves: her posture on public and private joint ventures and her views on key Bovespa component Petrobras, the energy giant: Will she continue to support fuel subsidies or will she support a policy to phase out these costly subsidies that burden the state-run company?
Besides getting approval from the business world, Silva, a devout evangelist, still has to win over converts among the Workers' Party and appease some who are skeptical about her social beliefs.
"I am afraid that we give a step back in social and cultural aspects," said Flávia Reckziegel, a 27-year-old actress. "There are important issues of equality like gay rights. ... I am afraid those ideas of equality could be forgotten."
—By CNBC's Silvana Ordonez