Brazilian President Dilma Rousseff's popularity has plummeted since the outbreak of nationwide protests several weeks ago, with the latest poll showing her approval rating has dropped 27 points in three weeks.
Thirty percent of Brazilians view her administration as good or excellent, one rating showed on Saturday. Just three weeks ago, that was 57 percent.
A quarter of people think her government is doing a "bad or terrible" job - up from nine percent since the last poll.
A survey published by the Datafolha polling centre said it was the largest drop in a president's approval rating since a 1990 fall for Fernando Collor de Mello, who was forced from office because of a corruption scandal.
The Folha newspaper surveyed 4,717 people on June 27 and 28. The poll had a margin of error of 2 percentage points.
The protests initially broke out in Sao Paulo targeting bus fare increases. They quickly spread nationwide and the causes expanded to include government corruption, high taxes, poor public services and billions of dollars spent on next year's World Cup football tournament.
Rousseff has responded by proposing a referendum on broad political reform and measures to upgrade public transport, education and health. Congress also rushed through measures to toughen penalties against corruption.
Rousseff faces her next presidential election in October of next year - three months after the end of the World Cup.
Al Jazeera's Adam Raney, reporting from Rio de Janeiro, said the cup would be decisive for Rousseff's political career.
"If the World Cup ends up in protests and confrontation we've seen, she may have a real tough fight on her hands", he said.