For over a decade, Nikolaj Hadjigenov has defended the victims of what he says are malicious prosecution and wrongful arrest by Bulgaria’s law enforcement authorities.

“They don’t defend the citizens. They only defend the government,” said the criminal defence lawyer and civil activist from his cramped office in central Sofia. “We have to change this.”

At elections this Sunday, Hadjigenov hopes that is exactly what will happen. Opinion polls indicate that Boyko Borisov, the conservative leader who has run Bulgaria for much of the past 12 years, will be consigned to the opposition and established parties will lose their grip on power.

“All the parties in Bulgaria are corrupt. They are only in it to take power and make money,” Hadjigenov said.

The lawyer is standing for parliament for Stand Up! Thugs Out!, one of three anti-establishment protest parties competing this weekend. The vote is likely to spell the end of Borisov era, a period in which, critics say, the former nightclub bouncer allowed corruption to flourish.

“It is highly improbable that Boyko Borisov will be able to form a government after these elections,” said Maria Popova, assistant professor at McGill University. “I think he’s done for.”

In an interview with the Financial Times, Borisov a former bodyguard to communist dictator Todor Zhivkov, seemed resigned to a spell in opposition.

He dismissed his opponents as communists beholden to mafia interests who were trying to “steal the elections or manipulate the results”. Yet he also cast any defeat as an opportunity to refresh, regroup — and return to power when his successors falter.

“I believe in two, three months they will have a total failure in their government,” he said.

Borisov’s GERB party, which is neck and neck with its closest rival in the polls, could still top the vote. Even so, it looks unlikely to be able to forge a stable coalition with either of the established parties, the socialists and the Turkish minority MRP, which have refused to work with him. That makes this weekend a potential turning point for Bulgaria.

“After so many years of this one very consolidated regime, it really feels like [we are] getting rid of the status quo,” said Vessela Tcherneva of the European Council on Foreign Relations in Sofia. “But it could take time to play out.”

Borisov oversaw a period of moderate economic growth in the EU’s poorest state, where Russia and Turkey vie for influence. As a member of the EU’s powerful centre-right European People’s party and a staunch ally of Germany’s Angela Merkel, he also kept EU funds flowing from Brussels despite Bulgaria’s rampant graft and mismanagement.

“The scale of corruption here is quite impressive,” said Ivan Krastev, chair of the Centre for Liberal Strategies. “It is not just about greed. It is about power.”

Boyko Borisov

Last year, simmering anger about corruption boiled over after photos appeared that seemed to show a pistol and wads of €500 notes on the prime minister’s nightstand. Borisov said the photos were doctored, but anti-government protests lasted several months.

Borisov rejects claims he oversaw rampant corruption, and told the FT his government had been “very disciplined” in spending EU money and clamped down on contraband.

But public opinion has continued to swing against him and his party. An interim administration, installed after an inconclusive general election in April, has won public support by exposing corruption and dismissing officials who enabled it.

Daniel Mitov, GERB’s deputy chair, also told the FT that the party “should have been more active in judicial reform” and that Bulgaria’s prosecuting authorities still had their “problematic” communist-era structure. “We have neglected this,” he said.

Highlighting that inaction, last month the US imposed sanctions on two Bulgarian businessmen and a security official for their involvement in corruption.

“There has been a general change in the mood and GERB has become toxic,” Tcherneva said.

Bulgaria has a record of abrupt political change fuelled by public anger over graft, voting twice since the end of communism to “throw out the bums and vote for newcomers”, Popova said.

In 2001, voters backed a government led by Simeon Saxe-Coburg-Gotha, who ruled before the second world war as Tsar and is formally known as King Simeon II. In 2009, it was Borisov who triumphed against the socialists on a law and order platform.

But this time there is no obvious opposition leader, and the protest parties may struggle to form a workable coalition without support from the established parties they claim to revile.

The largest protest party, There Is Such A Nation, is level pegged with the GERB in polls and could emerge the winner. It is led by Slavi Trifonov, a popular television presenter and singer. But he is not standing in the election and is believed to be in poor health. His policies are also vague and his candidates for parliament largely unknown.

“Once those people are elected, who knows how they’ll act,” said Hristo Ivanov, one of the leaders of Democratic Bulgaria, a reformist party backed by urban liberals. “It is a black box.”

Ivanov’s own party has the clearest agenda: judicial reform. But he also predicts an unstable reformist government, at best: “If we’re lucky we will have a small majority to govern. There is no guarantee it will be stable.”

For Hadjigenov, Bulgarians cannot wait for another political saviour to take power and rescue the country; opposition forces have to work together instead. “My dream is to kill corruption,” he said, gesturing to the case files of his defendants. “It’s a bloody war, and we need fighters.”