The survey of more than 2,500 people has a margin of error of plus or minus 2 percentage points.
Analysts attribute the drop to a sluggish economy in the last two quarters compared to last year's substantial growth and an ongoing corruption scandal implicating an ally of Lula's ruling Workers' Party.
Despite the president's plummet in popularity, Datafolha reported that if elections were held now, Lula would defeat all projected challengers.
Although the elections is still far off, those considered likely candidates against Lula are former President Fernando Henrique Cardoso and the 2002 candidate that lost to Lula, Sao Paulo Mayor Jose Serra.
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