Former President Rumen Radev has won Bulgaria's election by a landslide, sidelining long-dominant political forces and potentially pushing the EU and NATO member state closer to Moscow.

He will become the country's 21st Prime Minister since the end of communist rule in Bulgaria in 1990.

The performance, exceeding opinion poll forecasts, is one of the strongest results for a single party in a generation and may end, for now, the chronic instability that led to eight elections in five years.

Radev's Progressive Bulgaria party had 44.7% of the vote after 91.7% of ballots were counted, suggesting it could rule alone, but he has not ruled out a coalition with a pro-European group or a smaller party.

Progressive Bulgaria's tally put it far ahead of the pro-European We Continue the Change-Democratic Bulgaria (PP-DB) coalition with 13.2%, and the long-dominant GERB party, led by former Prime Minister Boyko Borissov, at 13.4%.

Who is Rumen Radev?

A eurosceptic and former fighter pilot opposed to military support for Ukraine's military effort against Moscow, Radev stepped down from Bulgaria's largely ceremonial presidency in January after nine years to run in the parliamentary election after mass protests forced out the previous government in December.

His new political movement rode a wave of frustration with political instability in the Balkan nation of 6.5 million, where voters are sick of corruption and veteran parties that have dominated politics for decades.

What does it mean for the EU?

Redev has criticized the European Union for relying too heavily on renewable energy.

But analysts do not expect him to try to reverse Bulgaria's adoption of the euro or to block wider EU aid packages to Ukraine.

On Sunday Radev said he would be willing to work on judicial reform with the PP-DB coalition and that Bulgaria would "make efforts to continue on its European path".

Bulgaria has developed rapidly since the fall of communism in 1989 and joined the EU in 2007. Life expectancy has risen sharply, unemployment is the lowest in the EU, and the economy has greater safeguards since adopting the euro.

But it lags EU countries in other metrics.

The cost of living has become a particular issue since Bulgaria joined the euro. The previous government fell amid protests against a new budget proposing tax increases and higher social security contributions.

"The country's main challenge is the economic crisis and the demographic crisis," said Tihomir Bezlov, a senior fellow at the Centre for the Study of Democracy in Sofia. "There do not seem to be many ideas in the winning camp on either of these issues."

Radev has been vague on policy and it is not yet clear how much he will change foreign policy in Bulgaria, a Black Sea nation on the EU's southeastern flank which joined the euro zone in January — a move Radev has criticised.

What does Radev's mean for the Russia-Ukraine conflict?

Radev, 62, is seen as a pragmatic, somewhat pro-Russian leader, who has criticised EU sanctions, and called for constructive dialogue with the Kremlin.

His campaign drew comparisons with Hungary's pro-Kremlin former Prime Minister Viktor Orban when he talked about improving ties with Moscow and resuming the free flow of Russian oil and gas into Europe.

Radev has long opposed the sale of the Bulgarian stockpile of Soviet era weapons to Ukraine but analysts in Sofia suggest he will allow Bulgarian arms exports via third countries, but ending direct support of military equipment from the Soviet era arsenal.

It's also thought unlikely he will wield the veto over EU funding like Orban did. 

Bulgaria has been an important supplier of ammunition and explosives to Ukraine through third countries. The Russia-Ukraine conflict has boosted the Bulgarian arms industry, particularly via the VMZ factory in Sopot and a €1bn joint venture with German arms company Rheinmetall.

What has been the reaction from Russia?

The Kremlin said on Monday that it was impressed by Radev's desire to resolve issues with Russia via pragmatic talks.

Asked on Monday by a reporter about purported panic in Europe over Radev's victory and whether Radev was a Russian "Trojan Horse", Kremlin spokesman Dmitry Peskov said:

"...We are, of course, encouraged by the words of Mr. Radev, who won the elections, as well as those of certain other European leaders, regarding their readiness to resolve issues through dialogue."

But Peskov said he thought it would be premature to draw wider conclusions about whether the overall political climate in Europe was changing given what he said were the usual statements - which he has in the past described as anti-Russian - emanating from the European Commission in Brussels.

How stable will Radev's government be?

Bulgaria's eighth election in just five years was expected to deliver more uncertainty, but instead it produced a clear political shift. 

Radev's landslide victory marks a dramatic break from years of fragmented parliaments and failed coalitions.

What appears to have made the difference this time is voter turnout. After a long period of political fatigue, more Bulgarians went to the polls, driven by the emergence of a new political force. 

That surge in participation translated directly into a strong mandate for Radev and his Progressive Bulgaria movement.

For his opponents, including Boyko Borisov, this election is a major setback. His GERB party, once dominant, now finds itself far behind, raising questions about its future role in Bulgarian politics.

Radev's critics have long accused him of holding pro-Russian views, particularly over his stance on European policies. But for many voters, his message of pragmatism and change appears to have resonated more strongly than those concerns.

That message was clear as he addressed journalists here in Sofia, calling for what he described as a more realistic approach to Europe's role in a rapidly changing world.

In his victory speech he explained: "What Europe needs right now is critical thinking, pragmatic actions, and good results, especially building a new security architecture."

With this kind of mandate, Bulgaria could now see something it has lacked for years – political stability.