Anti-government demonstrators set up a large inflatable doll in the likeness of Brazil's President Dilma Rousseff wearing a presidential sash with the words in Portuguese "Goodbye dear" and "Mother of big oil" written on it, in Sao Paulo, Brazil, Wednesday, May 11, 2016. Brazil's Senate is nearing a historic vote on impeaching Rousseff, likely ending 13 years of government by her party amid a spate of crises besetting Latin America's largest nation. (AP Photo/Andre Penner)

BRASILIA, Brazil - Brazil's Senate slogged toward a historic vote on impeaching President Dilma Rousseff early Thursday that would likely end 13 years of government by her left-leaning party amid a spate of crises besetting Latin America's largest nation.

If a simple majority of the 81 senators voted in favour, Rousseff would be suspended from office and Vice-President Michel Temer would take over for up to six months pending a Senate trial that would decide whether to remove her from office permanently.

Although Senate President Renan Calheiros had said he wanted the vote to take place Wednesday night, the sluggish pace of the debate made that impossible. By midnight, after 15 hours of debate, only 40 of the 70 senators scheduled to speak had made their addresses, meaning the vote itself would probably not come until around dawn Thursday.

"I'm asking for everybody's patience because we need to see this through to the end," Calheiros said at one point.

Under the rules of the impeachment process, each senator was allowed up to 15 minutes to speak, and many made full use of their moment in the spotlight — despite admonishments by Calheiros, who called on speakers to limit themselves to five to 10 minutes. That suggestion sparked anger from Rousseff's supporters, who insisted it was a bid to curb their freedom of speech.

Several thousand pro- and anti-government impeachers gathered outside the Senate, each group kept on opposite sides of a wall erected down the middle of the lawn. Small but intense clashes broke out between police and Rousseff supporters, with police using pepper spray and protesters throwing firecrackers at police lines. Emergency service workers took several people away after they fell ill with the effects of the clouds of pepper spray.

On the other side of the wall, a Carnival-esque spirit reigned, with pro-impeachment demonstrators sipping bans of beer while decked out in the yellow and green colours of the Brazilian flag.

While the impeachment measure was based on allegations that Brazil's first female president broke fiscal laws, the process morphed into something of a referendum on Rousseff and her handling of the country over the past six years.

Brazil is mired in the worst economic downturn in decades and a sprawling corruption scandal centred on the state-run Petrobras oil company has soured the national mood, even as the country gears up to host South America's first Olympic Games in August.

Supporters of impeachment blame Rousseff and her Workers' Party for the stalled economy and insist that Vice-President Michel Temer, whose party has split from the governing coalition, represents the only hope of reviving it.

"To improve the life of the nation we need to remove them (Rousseff's Workers' Party) at this time," Sen. Magno Malta told a scrum of journalists outside the Senate floor. "We will start to breathe again and the doctor will say the nation has given signs of life and will be stable soon."

When the impeachment was first floated just over a year ago, it seemed but a remote possibility. But the process snowballed, apparently unstoppably.

Only a simple majority of 41 votes was needed to suspend Rousseff for up to six months pending a trial in the Senate, and major newspapers tallied at least 50 likely votes in favour of impeachment.

Some pro-impeachment senators said they expected as many as 60 votes in favour of the impeachment, which would send a strong signal that Rousseff's faced a slim chance to emerge victorious from the trial and resume her mandate that ends in December 2018. In the event of a trial, at least 54 senators would have to vote against Rousseff to permanently remove her from office.

Polls have said a majority of Brazilians support Rousseff's impeachment, though they also suggest the public is wary about those in the line of succession to take her place.

Temer has been implicated in the Petrobras corruption scheme as has Calheiros, the Senate head who is now No. 2 in the line of succession. Former House Speaker Eduardo Cunha, who had been second in line, was suspended from office this month over allegations of obstruction of justice and corruption.

Rousseff has vehemently denied her administration's financial sleight of hand moves constituted a crime and argued that such manoeuvrs were used by prior presidents without repercussions. She has stressed that unlike many of those who have pushed for impeachment, she does not face any allegations of personal corruption.

The impeachment process, Rousseff says, amounts to a "coup" aimed at undoing social programs that have lifted an estimated 35 million Brazilians out of grinding poverty over the past years.

Temer, of the centrist Democratic Movement Party, denies Rousseff's claims that he would dismantle the popular social programs. Temer insists he actually would expand them, though he has also signalled that fiscal rigour is needed to dig Brazil out of the current hole.

Rousseff, a former Marxist guerrilla who was incarcerated and tortured under Brazil's 1964-1981 military dictatorship, was the hand-picked successor to her once wildly popular mentor, former President Luiz Inacio Lula da Silva. After handily winning the race to succeed him in 2010, she surfed his wave of popularity while the economy continued to prosper, but her approval ratings plummeted in step with the economy. She eked out a victory in the 2014 election, with 51 per cent of the vote.

To make matters worse, just as prices for commodities that are the lifeblood of Brazil's economy started tumbling, investigators began uncovering the multibillion-dollar kickback scheme at Petrobras.

While those ensnared in the scandal come from across the political spectrum, many of the people implicated are top officials in Rousseff's party, and that tarnished her reputation.

Rousseff "is the one who is having to pay for everything," said Sen. Telmario Mota de Oliveira, who argued the country's problems shouldn't be all pinned on the president.

The continuing probe has led to the conviction of dozens of the country's elite, from politicians to the former president of Odebrecht, a major construction firm.

Rousseff's prickly manner and her perceived reticence to work with legislators have also been blamed for alienating possible allies. Rousseff, however, has suggested that sexism in the male-dominated Congress has played a role in the impeachment.

The Senate action came after the lower house voted 367-137 last month in favour of impeachment, an anti-Rousseff verdict so resounding that many Brazilians believed it would influence the Senate.

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Associated Press writer Jenny Barchfield reported this story in Brasilia and AP writer Peter Prengaman reported from Buenos Aires, Argentina.

News from © The Associated Press, 2016