UPDATE 1-Brazil's Serra, falling in polls, needs TV boost
* New poll shows Serra 10 points behind Rousseff
* Serra will show experience, knock Rousseff achievements
* Likely hot topics are health, education, security (Recasts with new poll showing Serra trailing)
By Raymond Colitt
BRASILIA, Aug 5 (Reuters) - Brazil's ruling party presidential candidate Dilma Rousseff surged into her biggest poll lead on Thursday, piling pressure on her rival Jose Serra for a sterling performance in the first nationally televised debate.
Former Sao Paulo state Governor Serra, 68, who has debated in public since he was a student leader nearly 50 years ago, fell 10 points behind in the new poll as Rousseff gained from Brazil's robust economy and growing name recognition.
Just six months ago, Serra had a 20 percentage-point advantage in polls for the October election.
In the debate on TV Bandeirantes on Thursday night, Serra will try to regain momentum by playing up his experience and undermining Rousseff's role as energy minister and later chief of staff of President Luiz Inacio Lula da Silva.
But it will be a delicate balancing act for Serra, who boasts an Ivy League education and extensive managerial experience, given that the vast majority of Brazil's electorate is satisfied with the economy and Lula's government.
"He's got to challenge her without looking aggressive," said Valeriano Costa, a professor of politics at Unicamp. Serra already had an image as arrogant, Costa said.
Rousseff, a technocrat who has never stood for public office, will face the challenge of emerging from Lula's shadow and displaying a sometimes absent common touch. But the recent trend in polls clearly puts the pressure on Serra.
"Serra is more experienced in debates but it's difficult and he has more pressure to perform," said Costa.
Neither candidate is expected to depart far from Lula's mix of market-friendly policies and a strong state role.
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Until Thursday, most polls showed Serra either in a statistical heat with Rousseff, or trailing by 5 to 8 percentage points. Yet the new Sensus poll showed Serra losing badly in a hypothetical runoff against Rousseff, by a margin of 48.3 percent to 36.8 percent.
The margin of error in the Sensus poll was 2.2 percentage points.
In a country with a low penetration of print media, television is a particularly important campaigning tool, even though an important local soccer match could cut the debate's audience in Sao Paulo.
Aware she is less experienced than her rival, Rousseff has spent the better part of three days rehearsing for the debate.
Asked whether she was nervous, she responded the opposition candidates would need to take several tranquilizers. She had no problem discussing health issues with Serra, a former health minister, but would also focus on public security, an issue Serra had struggled with when he was mayor of Sao Paulo, Rousseff said.
"All Rousseff really needs to do in this debate is to play conservatively and avoid big mistakes," said Chris Garman, Latin America analyst with Eurasia Group consultancy. (Editing by Anthony Boadle)