Bulgaria's Socialists hope Sunday to win power and end years of dominance by karate-kicking former premier Boyko Borisov, in elections that could tilt the EU and NATO member more towards Russia.
The third election in four years in the European Union's poorest country could also see the nationalist United Patriots emerge as the third-biggest party and kingmaker in tough coalition talks.
Opinion polls put the centre-right GERB party of ex-firefighter Borisov neck-and-neck with the Socialist Party (BSP) on between 25 and 31 percent.
Some analysts distrust the polls however, saying that many voters are fed up with Borisov, 57, and may hand him a much worse result.
"There is always a great surprise in each elections here and maybe this time it will be a catastrophic loss for Borisov," analyst Evgeni Daynov told AFP.
Borisov, once a bodyguard for Bulgaria's last communist leader, was prime minister between 2009 and 2013 and again from 2014 and 2017. In between the BSP were in power for barely a year.
On both occasions the burly Borisov threw in the towel before his term was up, the first time after mass protests against poverty and corruption and most recently last November.
- Ninova's new impulse -
His latest resignation came after Rumen Radev, a former air force commander backed by the BSP, was unexpectedly elected president, seeing off Borisov's hand-picked candidate.
This was a major success for Kornelia Ninova, 48, who has energised the BSP base since becoming its first female leader last year.
If Ninova can become premier, this raises the prospect of Bulgaria, which has long walked a tightrope between East and West, drifting more towards Moscow.
Ninova has lashed out at Brussels, saying she is not content with Bulgaria being a "second-class member" of the EU and that she will veto an extension of sanctions on Russia.
Russia, with which Bulgaria has close cultural and economic ties, has also been accused of seeking to expand its influence in other Balkan countries in recent months.
"No one thinks Bulgaria is about to leave the EU or NATO," said political scientist Antony Galabov.
"But it risks becoming a representative for outside views and to become a Trojan Horse within these organisations."
But the more pro-EU Borisov has also said that he wants more "pragmatic" ties with Russia and to revive two joint projects -- a controversial gas pipeline and a nuclear plant.
- 'Bulgarian Trump' -
Forming a coalition will be difficult for either Borisov or Ninova, however, with as many as seven parties expected to have seats in a fragmented new parliament.
Both leaders have ruled out a tie-up with the main MRF party representing Bulgaria's Turkish minority, expected to garner between eight and 11 percent of the vote.
This leaves the United Patriots, a new anti-immigration, anti-Muslim grouping that includes the ultra-nationalist Ataka party and which could leapfrog the MRF into third place.
Another potential partner is Veselin Mareshki, 49, a colourful populist who likes being called the Bulgarian Donald Trump with promises to turn politics upside down and help the poor.
But many voters remained undecided amid widespread apathy in a country where the average monthly wage is just 500 euros ($540) even after a decade of EU membership.
"I will back neither Borisov nor his opposition Socialists. I do not believe them any more. I did not see any of their pledges materialising," teacher Tsvetomira Tosheva, 47, said in Sofia.
"I would rather vote for any of the new and still uncompromised faces, for some change, hoping it will bring something good."