BUDAPEST — With one year to go until Hungary’s next parliamentary election, Prime Minister Viktor Orbán’s greatest worry may not be pro-democracy protests or criticism from Brussels, but the influence of a man who knows him better than almost anyone else.

Oligarch Lajos Simicska, who went to high school with Orbán in the 1970s and later helped transform the Fidesz party from a group of university dormmates to the dominant force in Hungarian politics, has thrown his support behind the far-right Jobbik party.

“All my sympathies are with Jobbik,” the millionaire, who fell out with Orbán in 2014, told Hungarian news magazine HVG in April. “This is a stinking criminal gang that must go,” he said of his former friends, adding that if Jobbik does not defeat Fidesz, no one will.

Hungarians have come to refer to the rivalry as “the Orbán-Simicska war.”

But for Fidesz, the fight with Simicska is existential. Orbán’s political strategy over the past months has been to focus on refugee quotas. This approach has helped Fidesz keep liberal and left-leaning opponents weak, but cannot help Orbán compete with the equally anti-refugee far-right. Plagued by corruption scandals, Fidesz — which has been in power for seven years — is vulnerable to forces presenting themselves as outsiders.

Simicska did not answer multiple requests for comment for this article.

His change of allegiance is obvious in the streets of Budapest. Much of the city — indeed, much of the country — was plastered with Jobbik party billboards over the past few weeks, featuring straightforward slogans such as “You work. They steal.”

'Democratic again'

The campaign is financed by Simicska — who owns a major billboard company, along with a media and construction empire — and targets mainstream voters by portraying Jobbik as the people's party. Its efforts to compete with both Fidesz and left-wing parties revolve around its anti-corruption stance and focus on everyday economic issues like wages.

With Fidesz's popularity declining in the polls — the party has lost about half a million supporters so far this year, falling from 37 to 31 percent — and Jobbik taking aim at his credibility, there are signs that Orbán is nervous. If elections were held today, Fidesz would still be likely to win, but the prime minister is aware that many Hungarians — about 30 percent — are undecided. Jobbik’s popularity, meanwhile, has risen from 10 to 14 percent among all eligible Hungarian voters, according to polling firm Median.

Fidesz showed its lack of confidence in early June, when the Hungarian tax authority opened an investigation into Simicska’s billboard company. On June 23, after weeks of legislative maneuvering, parliament passed a law making it more difficult for political parties to receive discounted advertising space — designed to significantly limit Simicska’s ability to continue featuring Jobbik on his billboards across the country.

The far-right party has vowed to challenge the new law's constitutionality.

“Jobbik does not receive any support from Lajos Simicska,” the party’s leader, Gábor Vona, told POLITICO in an email. But the far-right politician added a caveat: “We have met twice so far at public events where we had a talk. There is one thing we agree on: Hungary must be made a democratic country again.”

'The smartest among us'

Like Orbán, Simicska was involved with the Fidesz party since the time of its founding in 1988. Until a few years ago, his name was nearly synonymous with that of Fidesz.

“Lajos was the smartest among us,” Orbán said in a 1988 interview.

A sophisticated political operative, Simicska shied away from the limelight. For the more than 25 years he was involved with the party, Hungarian media struggled to even get a photo of him. The eminence grise of Hungarian politics, Simicska almost never granted interviews.

“He was a strategist, organizer and chess-player type,” said Sándor Léderer, director of Hungarian anti-corruption watchdog K-Monitor, adding that Simicska had acted as a mentor to Orbán in their younger years.

Simicska quickly became the party’s money-man, responsible for securing funding for its operations. To develop Fidesz’s political machine, he also helped to found media outlets and other companies.

“The very Machiavellian approach of Fidesz comes partly from his approach,” said Léderer.

But the increasingly powerful Simicska was far from popular among his colleagues.

Simicska “was feared and disliked” within the party, said a senior Fidesz official, speaking on condition of anonymity.

“He was a misanthrope,” said the official, recalling that Simicska rarely showed up to Fidesz social gatherings and only had three or four allies in the party. “He was very close with Orbán.”

It was this personal relationship with Orbán, established in their teenage years, that enabled Simicska’s rise. When Orbán — known to prize loyalty above all else — first became prime minister in 1998, he chose to appoint his friend Simicska the sensitive position of head of Hungary’s internal revenue service.

Simicska “was feared and disliked” within the party, said a senior Fidesz official, speaking on condition of anonymity.

When Fidesz returned to power in 2010, Simicska’s media and construction empire boomed. According to Transparency International Hungary, in 2013, 11 percent of the value of public contracts went to companies connected to four Fidesz-affiliated individuals, with Simicska the most favored among them. That year alone, a construction company owned by Simicska won over 17 percent of tenders issued by the National Development Authority.

By 2014, Simicska’s allies held posts across the government administration. Politicians and business people looking to get their hands on a piece of the pie had to go through him, and he controlled what Hungarians read and saw on their television screens every morning.

Too powerful

But while distributing patronage among his closest allies is part of Orbán’s governing strategy, Simicska’s influence began to make him uncomfortable.

“Orbán was scared. … Simicska was getting too powerful,” said Attila Juhász, director of the Budapest-based Political Capital Institute.

Orbán’s fear that his old friend could present a threat to his own power led to a dramatic falling out, although the two sides differ in their retelling of what triggered the conflict.

The growing tensions burst out into the open in early 2015, when Simicska’s pro-Orbán employees resigned en masse and the oligarch — who for years had avoided the public stage — gave an expletive-laden interview about the prime minister in which he made his feelings toward his old friend very clear, describing him using a colorful expletive.

Orbán’s fear that his old friend could present a threat to his own power led to a dramatic falling out.

The conflict with Orbán had real financial consequences for Simicska, who lost millions as his companies began failing in government tenders and his media outlets no longer got state advertising.

In response, the oligarch turned his focus to preserving his business interests — and weakening Orbán in any way he can.

“Converting economic power into political power and political power back into economic power, that’s what matters to Simicska — he doesn’t care much about ideology,” said Juhász.

Not your typical feud

While Simicska has attempted to boost Jobbik’s position by supporting their billboard campaign, he doesn't shy away from supporting causes on the other end of the political spectrum if doing so will undermine Orbán’s interests.

In late April, journalists at independent liberal-leaning news site Index found out that Simicska had bought the site and transferred ownership to an association partially controlled by his associates. Index reporters agree Simicska hasn't interfered with their work thus far. Instead, his move is widely seen as an effort to prevent Fidesz-allies from taking control of the popular outlet.

Orbán’s allies, meanwhile, have worked hard over the past months to publicly discredit Simicska and his associates.

But many observers believe that Orbán’s conflict with Simicska is not just your typical political feud. As both sides attempt to delegitimize one another, their decades-long friendship and joint involvement with a party known for a vast range of corrupt dealings create the risk of mutually assured destruction.

But many observers believe that Orbán’s conflict with Simicska is not just your typical political feud.

For now, Fidesz is opting to answer Simicska’s campaign by turning accusations of corruption back on the oligarch. But as competition intensifies ahead of next spring’s parliamentary election, the fight is likely to get dirtier.

“As long as I’m here [...] I’ll continue the war,” Simicska warned after his falling out with Orbán. For Fidesz, the full implications of Simicska’s threat are now coming full circle.