• A leading candidate to become Slovakia's next prime minister, Robert Fico, has vowed to halt all military assistance to Ukraine.
• While observers are skeptical there will be a significant direct impact on the war from a Fico-led government, his leadership could add to recent pockets of discontent among EU countries over support for Ukraine.

Slovakia heads to the polls on Saturday for a general election that threatens to further fracture European Union support for Ukraine.

The main reason? A front-running contender to be its next prime minister has fiercely criticized Ukraine and the EU's anti-Russian position on the war, and vowed not to send "any arms or ammunition" to its eastern neighbor.

The central European country of 5.4 million people has been a staunch supporter of Ukraine since Russia's full-scale invasion in February 2022. However, Smer (translated as Direction in English) party leader Robert Fico — who served two prior periods as prime minister, from 2006 to 2010 and 2012 to 2018 — has vowed to change that.

It is set to be a close-run contest. A poll released Wednesday by research firm AKO for TV channel JOJ 24 gave rival party Progressive Slovakia the edge, with 18% of the vote to Smer's 17.7%; though other polls put Smer narrowly ahead.

There will be a plethora of issues besides Ukraine on voters' minds, from persistently high inflation and the cost of living to migration, health care and the political instability of recent years.

There is also a strong probability no party will get a majority in the 150-seat parliament, resulting in complex coalition negotiations and resulting uncertainty.

But international attention is largely focused on the extent to which Fico's return to leadership would change the geopolitical course of EU and NATO member Slovakia — at a time when Ukraine fears waning support among some of its allies.

Just rhetoric?

Fico's most recent period in office ended with his resignation amid mass protests over the murder of investigative journalist Ján Kuciak and his fiancée Martina Kušnírová, and over corruption in Slovak business and politics.

Smer, which Fico founded in 1999, is broadly left-leaning on economic issues. His previous leadership took Slovakia into the euro, in 2009.

Fico and his party have more recently embraced socially conservative, nationalist and anti-immigration rhetoric, and his stance on Ukraine has been extreme compared to his EU counterparts.

That has included blaming "Ukrainian Nazis and fascists" for the start of the direct conflict between Ukraine and Russia in 2014; accusing Slovakia's president of being a U.S. agent; describing the EU as a "war machine under the influence of the USA;" and arguing weapons deliveries to Ukraine have undermined Slovak sovereignty.

In more concrete terms, he has pledged to end all Slovak arms deliveries to Ukraine and resist plans for additional sanctions on Russia.

CNBC has contacted SMER for comment on the party's positions.

But despite Fico's proclamations, several analysts and observers say any short-term, tangible impact on Ukraine may be limited.

"Although Slovakia was one of the first EU/NATO countries to pledge to provide Ukraine with Soviet-era MiG-29 fighter jets and an S-300 air defence system in 2022, it has only a limited weapons stocks available for transfer to Ukraine in the first place," Tatiana Valyaeva, a consultant at London-based Control Risks, told CNBC.

"Furthermore, given Slovakia's challenging economic situation and the economic significance of the arms industry, it is unlikely that Fico would cut arms deliveries to Ukraine. The city of Košice in the country's less affluent eastern region also hosts a lucrative facility for repairing military equipment for the Ukrainian armed forces."

Fico showed pragmatism in his previous terms and largely avoided conflicts with partners in the EU and NATO, Valyaeva added.

Wider trend

However, Valyaeva also noted that any shift in rhetoric could contribute to undermining international solidarity with Ukraine.

Slovakia's relations with the embattled country have soured in recent months independently of the election, amid a dispute over agricultural trade.

Ukraine last week filed a complaint with the World Trade Organization against Slovakia, Poland and Hungary after the three introduced import bans on a range of Ukrainian products, as they argued the move was necessary to prevent a supply glut that will drive down prices and harm local farmers.

Trading of critical comments by officials on both sides escalated the dispute, with Poland saying it will no longer supply Ukraine with weapons.

Hungary's right-wing Prime Minister Viktor Orbán, meanwhile, staunchly claimed the move was necessary to protect the countries from a "flood" of imports while officials in Brussels "turn... a blind eye." Although Olga Bychkova, an economist at Moody's Analytics, noted that the strength of harvests in Latin America, Europe and the U.S. significantly outweigh the impact of Ukrainian exports on wheat and corn prices.

Orbán and a number of his officials have been consistently critical of EU measures regarding the war, both on aid for Ukraine and sanctions against Russia.

Alena Kudzko, vice president for policy and programming at Slovak think tank Globsec, believes Fico could prioritize domestic interests over taking a contrarian stance on the global stage.

Nonetheless, "it may prove more difficult for the EU and NATO to forge unified foreign policy positions on Ukraine and Russia," and the "Slovak government could become a troublemaker willing to veto policies, protract discussions, and impede foreign policy decisionmaking frequently and profoundly," Kudzko wrote in an article for Carnegie Europe.

Control Risks' Valyaeva also noted: "While only Hungary currently boasts an openly pro-Russian government, in countries such as Germany, France, and Spain, populist parties sceptical of Ukraine support are gaining traction."

"Several of these nations are approaching national or regional elections that have the potential to sway public sentiment toward Moscow. This emerging wave of political dynamics holds the potential to influence Ukraine's position in negotiations with Russia."