Updated

Some 6.8 million Bulgarians are eligible to choose their new parliament in an election widely predicted to fail to determine a clear winner, leading to a political deadlock instead of a new government.

This will be the third parliamentary vote since 2013 and follows the resignation of the center-right government of Boiko Borisov over the defeat of its candidate in the November 2016 presidential vote.

The current election campaign has focused mainly on the future of the European Union, the influence of Russia and Turkey on domestic politics and the threats from a possible rise in migrant inflows.

Populist and radical nationalist rhetoric has dominated the campaign and polls suggest a strong showing of populist and nationalist parties.

At least six parties are tipped to make it into parliament, likely producing another fragile coalition. Polls show the top two parties running neck-and-neck. Here is a look at the main contenders:

GERB

The key player in these elections is former Prime Minister Boiko Borisov, 57, a political maverick who has managed to combine his man-in-the-street rhetoric with a strict obedience to Brussels, which has ensured him support at home and abroad.

It has helped him win all but one election after he formed his center-right GERB party in 2006 and turned it into the country's most influential party since the fall of communism.

Borisov headed a minority government between 2009 and 2013, when he resigned amid sometimes violent protests against poverty, high utility bills and corruption. Last November, Borisov resigned for a second time after his party candidate was defeated in the presidential race.

Halfway into its four-year term, Borisov's coalition government had managed to restore political stability after months of anti-corruption protests. But its popularity had faded because of the slow pace of reforms to eliminate graft and poverty, and overhaul the judicial system.

SOCIALISTS

Latest surveys suggest that Borisov's party is level with the Socialist Party of ex-communists led by Kornelia Ninova, who has managed to raise support after she became its leader a year ago. Last November, former air force general Rumen Radev, who ran on the Socialists' ticket, defeated Borisov's party candidate in the presidential vote.

Riding high on the wave of Radev's victory, the 48-year-old Socialist leader is trying to convince supporters that their time has finally come to regain power.

The Socialists favor a bigger role for the state in the economy and Ninova has used the campaign to rally the party hardcore voters with promises for higher salaries and pensions. She also wants the EU to lift sanctions against Russia, and plans to restart a nuclear energy project.

NATIONALISTS

The United Patriots alliance, formed ahead of the presidential vote by the Patriotic Front and the Ataka party, is expected to secure a solid chunk of the vote.

Their presidential candidate, Krasimir Karakachanov, came in third last November with some 15 percent of the votes due to widespread fears of a massive refugee influx.

Now, support for them may get an additional boost after they staged protests against what they call Turkey's "meddling" in the elections. The nationalists claim that Turkish officials were forcing expatriate voters to support a pro-Ankara party, which they say is a threat to Bulgarian national interests.

A newcomer to the parliamentarian elections is Veselin Mareshki and his party Volya (Will). He made a star debut in the presidential race by winning 11 percent of the votes. Dubbed by many as the Bulgarian Donald Trump, the 49-year-old wealthy businessman has gained popularity with his anti-establishment and patriotic rhetoric and promises strict immigration controls and friendlier relations with Moscow.

TURKS

Bulgaria's sizeable Turkish minority is represented by the Movement for Rights and Freedoms and the party DOST, which split from it last year.

Alleged support from Turkey's government for DOST has fueled tensions between Bulgaria and Turkey in recent days. Bulgaria criticized Turkey, saying its officials were interfering in Bulgaria's internal affairs by calling on people to vote for a particular party. Turkey retorted that ethnic Turks were facing "pressure" to vote a particular way.

Some 10 percent of Bulgarians are of Turkish origin. More than 300,000 have settled permanently in neighboring Turkey but still hold Bulgarian passports and are eligible to vote in Bulgaria.

RIGHT-WING PARTIES

The right spectrum of politics is represented by three groups, but only one of them is tipped to make it into parliament — the Reform Bloc, which was part of Borisov's coalition government.