Russia is the dominant topic as Bulgarians prepare to go to the polls to pick a new president.

The two favorites to come out on top in Sunday's presidential election are lobbying for the lifting of EU sanctions on Russia, while the sitting president warns of Moscow's growing influence in the country.

Tsetska Tsacheva, the candidate of Prime Minister Boyko Borisov's center-right government, and Rumen Radev, a former air force commander backed by the opposition Bulgarian Socialist Party (BSP), are likely to win the most votes on Sunday and face a runoff on November 13.

Tsacheva has been ahead in the polls for months but Radev has narrowed the gap. The latest polls indicate that Radev would narrowly win the runoff.

The outcome of the likely runoff will be determined by the supporters of those eliminated in the first round of voting.

The two are part of an eclectic mix of 21 candidates in the race to succeed Rosen Plevneliev, including Biser Milanov, a former convict whose nickname is “the Stain,” and Yordanka Koleva, a “clairvoyant” who has made outlandish claims about friendships with Russian President Vladimir Putin and former U.K. Prime Minister Tony Blair.

Plevneliev told the BBC on Friday that Putin is working hard to divide Europe and Russia, adding that the two sides are involved in a "dangerous and unpredictable" confrontation he dubbed the "Cold Peacetime." Plevneliev is not seeking reelection and will step down in January.

Krasimir Karakachanov, backed by a group of nationalist and right-wing parties, is polling a distant third, after gaining traction by beating the drum of illegal migration on the campaign trail.

Traycho Traykov, the candidate of the Reformist Bloc, the junior government coalition partner, is among several vying for fourth spot. Others are former Foreign Minister Ivailo Kalfin of the Alternative for Bulgarian Revival, which broke away from the Socialists; Plamen Oresharski, a former prime minister who has the support of the Movement for Rights and Freedoms, a party which relies on Bulgaria's Turkish and Muslim communities; and businessman Veselin Mareshki.

Bulgaria was one of the Soviet Union’s most obedient satellite states, and many Bulgarians still feel a cultural and historical affinity with Russia. Both Radev and Tsacheva have tried to balance their country's interests between Brussels and Moscow, asserting that Bulgaria's NATO and EU commitments do not preclude a rapprochement with Moscow.

Radev, a non-political party figure with BSP backing, told Reuters last month that Bulgaria is not looking for an alternative to its membership in NATO and the EU. On the other hand, "we should not look on Russia as an enemy," he said. "Europhillia does not mean Russophobia," he added and warned that anti-Russian rhetoric carries "unnecessary risks.”

Tsacheva, who has made no secret of the fact she was a member of the Communist Party, was even more cautious, saying that both Bulgaria and the European Union "have an interest in a dialogue with Russia.”

Dimitar Bechev, an expert on Russian policy in the Balkans at Harvard University, said Tsacheva and Radev differ little in their approach to Moscow. But he said electing Radev would be a signal that "Bulgaria [is] drifting toward Moscow.”

However, Solomon Passy, a former foreign minister who negotiated the country's EU and NATO membership agreements, said that “Bulgaria’s pro-Western orientation is in progress.” Sunday's election would be decided on domestic issues, not Bulgaria’s international alignment, he said, adding that neither Tsacheva nor Radev would divert the country from its pro-Western path.

Kristian Vigenin, a former foreign minister and now foreign affairs secretary of the BSP, said most Bulgarian politicians agree that EU sanctions on Russia have been inefficient, damaging the Bulgarian and Russian economies without changing Moscow's course.

“Isn't it a natural step to reconsider this approach and try something new, more likely to produce results?” Vigenin said. He defended Radev’s claims that Crimea is “de facto” part of Russia and said there's no contradiction in the BSP-backed candidate's pledge of allegiance to European values and NATO principles.

“We could continue to repeat endlessly that Crimea is part of Ukraine, but as we speak it is being further integrated within Russia in economic, social and political terms. How are we going to deal with that?”

Referendum on Borisov

The outcome of the likely runoff will be determined by the supporters of those eliminated in the first round of voting.

Radev is likely to win over left-leaning voters, but also many of those disappointed with Borisov, which could turn the election into a referendum on his leadership.

If Tsacheva does become president, Borisov may look to reward the support of his rivals by moving to the right on migration.

The EU and U.S. welcomed Borisov's return to power in 2014 following Oresharski’s brief spell at the helm.

However, it has been marred by protests over Oresharski’s appointment of the politician and businessman Delyan Peevski as head of a beefed-up intelligence service. Critics say that Borisov, a former bodyguard, has been unable – or unwilling – to break up powerful networks of political and business interests in Bulgaria, including one allegedly led by Peevski.

That gives even some ardent opponents of the BSP hope that a Radev victory could break Borisov’s grip on power. If Radev wins, an early election — the third in five years — is very likely, according to Otilia Dhand, vice president of Teneo Intelligence. That could lead to months of uncertainty, and probably end in “another hung and fragmented parliament,” she said.

Borisov has said he will only stand down if Tsacheva is knocked out in the first round. His Citizens for the European Development of Bulgaria — known by its Bulgarian acronym GERB — has a 10-point lead over the BSP in the polls, but is unlikely to win a majority in an election.

Even if Tsacheva wins, Borisov may look to reward the potential support in the presidential runoff of politicians like Karakachanov, which could mean swinging to the right on migration; or the DPS, which would “kill hopes of reform,” said Bechev, the Balkan expert.

This story has been updated to clarify an expert's quote.