SAO PAULO (AP) — Public approval of Brazilian President Dilma Rousseff's government has suffered a steep drop in the weeks since massive protests broke out across this country, according to Brazil's first nationwide poll released since the unrest began.

For the first time, polling shows she would be forced into a second-round runoff vote in next year's presidential election.

Published Saturday by Folha de S. Paulo, the country's biggest newspaper, the Datafolha survey found 30 percent of respondents rated Rousseff's government as "great/good," a sharp fall from the 57 percent who gave it that rating three weeks ago before the demonstrations began.

The government's popularity was down throughout the country, including in the northeast where the ruling Workers Party is strong. Her rating dropped there from 64 to 40 percent there.

The poll also found that 30 percent of voters say they'll cast their ballot for Rousseff in October 2014 — that is down from 51 percent just a few weeks ago.

If no candidate wins an outright majority, a second-round vote is held between the top two vote winners.

In the Datafolha poll, that second-round candidate would be Marina Silva, a former Workers Party environment minister who split with the party in 2009 over policy differences and joined the Green Party. She ran for president in 2010 and won a surprising 20 million first-round votes, but it wasn't enough to get her to the second-round ballot.

In the most recent poll, 23 percent of respondents said they'll vote for Silva, up from 16 percent a few weeks ago.

Datafolha interviewed 4,717 people on June 27 and 28, and the poll has a margin of error of 2 percentage points.

The government's approval rating had hit 65 percent in March, according to Datafolha, but in June suffered its biggest drop since Rousseff took office 2 ½ years ago. Many Brazilians have been upset about rising inflation and shrinking purchasing power.

The firm said the government's approval had suffered the biggest drop for any president since a 1990 fall for then-leader Fernando Collor de Mello who tried to control spiraling inflation by freezing all savings accounts. He was forced from office because of a corruption scandal two years later.

Beginning mid-June, the recent protests had first targeted transportation fare hikes but quickly expanded to a variety of causes including government corruption, high taxes, poor public services and the billions of dollars spent for next year's World Cup soccer tournament and the 2016 Olympics in Rio de Janeiro. The Datafolha poll showed that 81 percent of respondents supported the protests.

Political watchers said Rousseff's popularity drop was to be expected in the face of the biggest protests this 197 million-person nation has seen in two decades.

"The protest movement that began two weeks ago isn't necessarily a movement against the (ruling) Workers Party nor Dilma personally, it's a protest against the entire ruling class," said Pedro Arruda, a political science professor at the Catholic University of Sao Paulo. "If polled, the unpopularity would be of all politicians. The people are protesting all the parties."

For Rio de Janeiro Mayor Eduardo Paes, the demonstrations have underscored the "institutional crises" affecting the country's political parties.

"Which party has a good image?" he asked in an interview in Saturday's edition of Folha de S.Paulo. "Only the one not yet been born. We cannot sit back and think there is nothing more to be done because we have become a democracy, pulled 40 million people out of poverty and enjoy high employment rates.

Throughout the protests, the country has been hosting the Confederations Cup soccer tournament, which are seen as a warm-up to next year's World Cup. But the unrest has grown to such a level that Rousseff and other political leaders have reportedly decided not to attend Sunday's final match, which would be seen as a major embarrassment after they had showcased the country's hosting of such mega-events as proof that Brazil had finally arrived on the global stage. Even football legend Pele says he won't attend the match. Demonstrators are expected to turn out around the iconic Maracana stadium where the Brazilian and Spanish teams will meet.

Meanwhile, social networks were abuzz with rumors of a general strike Monday, with posts saying it would hit every state. However, representatives for Brazil's two biggest unions, the Central Workers Union and Union Force, said they knew nothing about such a strike but were planning a national work slowdown for July 11, when workers will only perform strictly what's required of them on the job.

Rousseff is expected to deliver a formal proposal to Congress early next week on a political reform plebiscite she wants held in the coming months. She hasn't yet released any details on what political reforms she will suggest nor how or exactly when a plebiscite would occur.

Earlier this week, the president announced $23 billion in transportation investments. On top of that, she said her government would prioritize improvements in fiscal responsibility, controlling inflation, political reform, health care, public transport and education.

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Associated Press writer Bradley Brooks contributed to this report from Sao Paulo.