President Dilma Rousseff's popularity has nosedived since Brazil's nationwide street protests erupted, a poll said Saturday as Rio braced for more demonstrations coinciding with the Confederations Cup final between the national squad and Spain.

A Datafolha poll said Rousseff's approval rating has plunged from 57 percent down to 30 percent since June 6-7.

News reports say she is skipping Sunday's football game to avoid the prospect of being jeered.

The poll added that the percentage of people who think her government is doing a "bad or terrible" job has risen from nine to 25 percent since.

In March, Rousseff's popularity stood at 65 percent.

This month her approval rating dipped in all regions, according to the survey of 4,717 people conducted in 196 cities.

The latest poll, which has a margin of error of two percentage points, comes as a wake-up call for Rousseff and her ruling leftist Workers Party ahead presidential voting scheduled for October 2014.

"We expected this fall. It is serious for the government. The president has been weakened at a time when the economy is not performing well," said Andre Cesar, an analyst with the Brasilia-based consulting firm Prospectiva.

The protests initially broke out in Sao Paulo more than two weeks ago over increases in mass transit fares. But they quickly spread nationwide and mushroomed into a public outcry over substandard public services and the high cost of Brazil's hosting next year's World Cup.

The hundreds of thousands of Brazilians who have taken to the streets have also been demanding an end to rampant corruption among politicians.

The protests have been largely peaceful but have at times been marred by clashes with police and acts of vandalism.

They coincide with the ongoing Confederations Cup, a dry run for the World Cup which Brazil will also host next year for the first time since 1950.

On Sunday hosts Brazil face Spain in the tournament's final in Rio's iconic Maracana stadium.

Press reports said Rousseff decided not to attend the match as she might become the target of protests outside and inside the stadium.

Two weeks ago, the president was booed by demonstrators as she attended the opening game of the cup in Brasilia.

Several demonstrations are planned across Rio Sunday and are to converge on the Maracana stadium.

Some 6,000 police will be deployed around the arena and road access to it will be severely restricted, officials said.

They urged fans to use public transport to reach Maracana.

Friday, Rousseff scrambled to build support for sweeping political reforms in response to the country's biggest social turmoil in more than 20 years.

Throughout the week, she huddled with members of civil society, elected officials and union and party leaders to put the finishing touches on a proposed plebiscite on political reform she hopes to submit to Congress as early as Tuesday.

Officials from the Higher Election Tribunal said the plebiscite may have a price tag of nearly $250 million.

The government wants the political reform to be in place in time for next year's presidential elections, in which Rousseff will seek another term.

Congress meanwhile rushed through bills to toughen penalties for those found guilty of corruption.

And lawmaker Natan Donadon, who was sentenced to 13 years in jail in 2010 for embezzlement -- Friday surrendered to authorities after the Supreme Court ordered his immediate detention, the first such move in 25 years.

Meanwhile the country's labor unions scheduled strikes and demonstrations for July 11 to keep up pressure on the government.