By Brad Haynes
SAO PAULO (Reuters) - Brazil's President Dilma Rousseff has regained the momentum in an election race that looks too close to call just a week before the first round of voting, using a wave of attacks to halt a surge by challenger Marina Silva.
In a campaign blitz, Rousseff is pressing her huge advantage in fundraising and TV time to undermine support for Silva, a lifelong environmentalist who surged in polls after joining the race late but has many voters still sizing her up.
The leftist president is likely to win most votes in the first round of voting on Oct 5 and polls show her and Silva running neck and neck in a widely expected runoff three weeks later.
Earlier polls had shown Silva with a strong lead in the runoff but Rousseff's more than five-to-one advantage in fundraising and advertising has given her a platform for relentless attacks questioning Silva's readiness for the presidency and commitment to unpopular policies.
"Turn right. Recalculating. Turn left. No, I changed my mind - to the right," says a woman's voice, mimicking a GPS navigator, in a radio ad mocking changes to Silva's platform. "If as a candidate Marina is always changing directions, imagine as a leader."
Still, Rousseff could lose the upper hand in the second round. Both candidates will get equal television time and Silva is expected to attract more supporters of the candidates eliminated in the first round.
"This is going to be the toughest campaign in more than two decades," said political analyst Andre Cesar. "There's no clear advantage in the second round. It's wide open."
Rousseff's strategy has been to play on voters' uncertainty about Silva, who represented three political parties in the last five years and tried unsuccessfully to create a new one.
Silva only moved to the top of the Brazilian Socialist Party's ticket last month when its original candidate, Eduardo Campos, died in a plane crash.
Nearly three in four voters are sure they will vote for or against Rousseff, while just 53 percent have made their mind up about Silva, according to a survey this week by pollster Ibope. That means support for Silva has more potential upside, but it is also less stable.
FEAR OF LOSING GROUND
Rousseff has built her campaign on 12 years of Workers' Party rule during which the economy grew nearly 50 percent, pulling more than 30 million people out of poverty and pushing unemployment to record lows.
"Dilma is running on the fear of losing those advances from recent years," said Thiago de Aragão, a partner at the Arko Advice political consultancy. "But the country is divided. A lot of people are tired of the present and want a brighter future."
Growth has fizzled since Rousseff took power in 2011 as uncompetitive industries, higher inflation and heavy-handed government policies eroded the confidence of investors and consumers.
Silva, who left the Workers' Party in 2009 after quitting as environment minister, has set forth a detailed platform calling for more sustainable development, orthodox economic policies and cleaner politics.
Her anti-establishment tone has struck a chord with voters sick of corrupt politicians and poor public services.
But the details of Silva's platform have provided easy fodder for slick and often misleading attack ads, which doubled her rejection rate among voters in a month to 22 percent of the electorate, according to pollster Datafolha.
"We feel the wind has shifted in our favor," a senior government official told Reuters, adding that Rousseff's humor has improved over the course of the month as polls showed her re-election chances improving.
The sentiment in financial markets has gone the other way. Brazil's stock market rallied 12 percent in just three weeks when Rousseff looked headed for defeat but has given up those gains as the race drew even.
Many investors are hoping for more predictable economic policies and less state intervention under a new president.
Momentum could easily swing again in what has been a topsy-turvy campaign. Televised debates on Sunday and Thursday will give the candidates a fresh chance to shake up the race.
Voters are clearly restless, with a wide majority hoping the next government will try a new direction. Even Rousseff's campaign slogan is a pledge to "change more," but one third of voters say there is no way they will vote for the president, leaving an opening for a strong challenger.
'THE OTHER CHEEK'
Silva has decried the president's negative campaigning and promised to take the moral high ground.
"Our strategy for the final week is to keep telling the truth, without resorting to savage marketing," Silva said in an interview with Reuters on Thursday. "We're going to turn the other cheek."
She has had little choice. Under Brazil's electoral laws, Silva's team gets just two minutes of electoral programming on nightly television, barely enough time to defend her and outline new proposals let alone criticize her opponent's record. With 11 minutes of campaign programming, the president has room to do all three.
If Rousseff and Silva advance to the second-round vote on Oct. 26 as expected, they will both have 10 minutes of TV time every night.
To avoid a runoff, Rousseff would have to win more than 50 percent of votes in the first round, something polls suggest is unlikely. After that, the top two candidates will get three weeks for a head-to-head campaign, erasing many of the incumbent's advantages.
In that phase, Silva could also make up ground in fundraising as corporate donors that have favored Rousseff's party reposition themselves for a potential Silva victory.
The biggest second-round boost for Silva would come from consolidating the opposition vote that is now divided between her and third-place candidate Aecio Neves, an investor favorite facing long odds of advancing past the first round.
Neves has opened a second flank against Silva in recent weeks, arguing she remains too close to the Workers' Party to represent real change. That has peeled away some first-round votes but, even without an official endorsement, most of Neves' supporters are expected to back Silva in the second round.
Undecided voters have dwindled to about 5 percent of the electorate, and analysts say they may also break toward the challenger in the final days of the race.
"You've had years to decide if you're going to support the president, but you've only had a few weeks to consider her rival," said political consultant Aragão.
(Additional reporting by Brian Winter in Brasilia and Paulo Prada in Rio de Janeiro; Editing by Todd Benson and Kieran Murray)