By Jan Lopatka

BRATISLAVA, Oct 1 (Reuters) - Robert Fico, who won Slovakia's parliamentary election on Saturday by appealing to anti-western and pro-Russian sentiment, may lead the European Union nation for the fourth time after once again shifting political gears to appeal to a changing electorate.

During a three-decade career, Fico, 59, has skilfully weaved between pro-European mainstream and nationalistic anti-Brussels and anti-American positions while showing a willingness to change course depending on public opinion or changed political realities.

He has remained steady throughout his career, however, on promises to protect living standards of those left behind in a country where living standards for many are only slowly catching up to western Europe and where many hold relatively fond memories of a communist-era past.

"Fico is a technician of power, by far the best in Slovakia. He does not have a counterpart at the moment," said sociologist Michal Vasecka, from the Bratislava Policy Institute.

"Fico is always following opinion polls, understands what is happening" in society.

Yet Fico has embraced more extreme positions over the past four years that include attacks on western allies, pledges to stop military support for Kyiv, criticism of Russian sanctions and threats to veto any future NATO invitation for Ukraine.

His campaign call of "Not a single round" for Ukraine appealed to voters in the nation of 5.5 million where only a minority in the NATO member country believe Russia is at fault for the Ukraine war.

Fico, who analysts see inspired by Hungary's Viktor Orban, has said he has Slovak interests at heart and wants the war to end. Western allies and Ukraine say halting military aid to Kyiv would only help Russia.

"We see Viktor Orban as one of those European politicians who do not fear to openly defend the interests of Hungary and Hungarian people," Fico told Reuters in emailed responses last month.

"He puts them in the first place. And that should be the role of an elected politician, to look after the interests of his voters and his country."

Fico has also railed against the country's liberal president, Zuzana Caputova, who sued him last month for spreading lies about her. He has labelled various opponents and NGO's as following instructions of U.S financier George Soros.

Born to a working-class family, Fico graduated with a law degree in 1986 and joined the then-ruling Communist party.

After the 1989 fall of Communist rule, he worked as a government lawyer, won a seat in parliament under the renamed Communist party, and represented Slovakia at the European Court for Human Rights.

Fico has run SMER-Social Democracy party since 1999 after establishing it to oppose the reformist centre-right cabinet.

He parlayed dissatisfaction with liberal economic reforms into his first election victory in 2006.

But he also kept the nation on course to adopt the euro in 2009 despite forming a government with nationalists.

His second cabinet won after another centre-right coalition broke up two years later, and a tough stance against migrants helped him win re-election in 2016. After that win, he declared he wanted Slovakia as part of the EU's core with France and Germany.

Those shifts in the past have given belief to foreign diplomats that he may find a pragmatic way with European and NATO partners again, especially given that a far-right party he may ally with under some scenarios did not win any seats on Saturday.

Fico's political fortunes faded in 2018 when journalist Jan Kuciak, who was investigating high-level graft, and his fiancee Martina Kusnirova were killed by a contract killer.

This fuelled mass protests against graft and Fico was forced to resign. SMER lost power in a 2020 election to parties pledging to weed out corruption, and his party split.

Polling under 10%, Fico once sought to address voter fears during the coronavirus pandemic when he slammed government health measures.

"He became the most prominent political representative of a movement against face masks or vaccination," said political analyst Grigorij Meseznikov.

At the same time he a tapped into dissatisfaction with bickering in the ruling government and raised doubts with its pro-western course, chiming with pro-Russian narratives on social networks that had spread across Slovakia.

Fico also swatted away accusations of graft that have dogged his party during his political career. He was charged with criminal conspiracy in 2022 to use police and tax information on political foes -- charges he denied and which were later dropped. (Reporting by Jan Lopatka, Editing by Michael Kahn and Michael Perry)