Thousands of demonstrators have arrived at the central plaza in Brazil’s capital for Independence Day celebrations in support of embattled president Jair Bolsonaro

Mass participation in rallies scheduled across the country would reinforce the right-wing leader’s push to prove he is a strong candidate for re-election next year – despite slumping poll ratings – and could help him recover momentum after a string of setbacks.

He also seeks support in his feud with the Brazilian supreme court, which has been probing his allies over allegedly organising anti-democratic acts and spreading false information.

The demonstrations carry the risk of violence that could be perceived as stemming from the president’s influence.

Critics fear Mr Bolsonaro could be preparing a Brazilian version of the January 6 riot in Washington, where supporters of former American president Donald Trump stormed the US capitol, alleging he had been robbed of a re-election victory.

Already, Mr Bolsonaro has said he might reject the 2022 election results if he loses.

Tens of thousands of people had already arrived in convoys of trucks and buses to Sao Paulo and the capital, Brasilia, where Mr Bolsonaro is expected to speak at the two largest rallies.

The mood on Monday at the Brasilia campsites was of anticipation, with bottles of beer passed around portable grills, but a general reluctance to speak with journalists reflected underlying tension.

On Monday evening, supporters broke through police lines set up to block vehicles and halt early pedestrian access to the capital’s central mall.

Video on social media showed trucks advancing while blaring their horns as hundreds of people dressed in the national green-and-yellow colours walked alongside and cheered.

By morning, dozens of honking trucks were parked on the mall, where only pedestrians were supposed to be allowed.

Security around the supreme court was reinforced early on Tuesday at its own request, according to the press office of one of its justices, Luiz Fux.

Mr Bolsonaro’s government has been beset by crises that his critics say were at least partly self-inflicted.

The nation’s Covid-19 death toll of more than 580,000 is the second highest in the world, and eighth highest on a per capita basis. A congressional investigation of the government’s response has produced several accusations of wrongdoing.

Inflation – traditionally the Brazilian bogeyman for presidential approval ratings – is approaching double-digits, with higher costs for mainstays like food, gasoline and electricity.

And power prices are expected to rise more due to dwindling hydroelectric reservoir levels that were ignored for months.

There may be energy rationing in store, further hindering any economic rebound.

The result has been a slide in Mr Bolsonaro’s approval ratings, accompanied by a steadily climbing percentage of people saying they would never vote for him.

Polls show his nemesis, former president Luiz Inacio Lula da Silva, could trounce him in a runoff next year if he enters the race.

Mr Bolsonaro has set out to prove them wrong with Tuesday’s demonstration, whose organisers promised: “September 7 will be gigantic!”

Mr Bolsonaro said Sunday that he plans to address two million people in Sao Paulo. A crowd that size has not gathered there in five years, when people demanded then-president Dilma Rousseff’s impeachment.

Tuesday’s demonstrations “may show that he has millions of people who are ready to stand up and be with him even when Brazil’s economy is in a bad situation, inflation near 10%, the pandemic, and all that,” said Thomas Traumann, a political analyst.

“If Bolsonaro feels he has the support of millions of Brazilians, he will go further in his challenging of the supreme court,” Mr Traumann added,

Some centrist allies have implored the president to rein in his rancour when addressing crowds to avoid jeopardising support from moderate voters and legislators.

Mr Bolsonaro said last week that “no-one need fear September 7” – but the next day he portrayed the event as a make-or-break “ultimatum”.

Days earlier, outside an evangelical church, Mr Bolsonaro said the only options for his future are to be victorious or die trying.

He has repeatedly claimed the supreme court is too powerful, violating constitutional limits, raising fears among critics of a man who has frequently expressed nostalgia for the nation’s past military dictatorship.

He has requested that the senate should impeach a supreme court justice who has jailed several of his supporters for allegedly financing, organising or inciting violence or disseminating false information.

On the eve of Tuesday’s protest, Mr Bolsonaro also signed a provisional measure sharply limiting social media platforms’ ability to remove content, restrict its spread or block accounts.