(Bloomberg) -- Politics is defined by rivalries, but rarely do they come as bitter as the one between the most powerful man in Poland and his nemesis.

For ruling party leader Jaroslaw Kaczynski, the summer return of former Prime Minister Donald Tusk to spearhead Poland’s opposition has reignited an enmity that’s deeply personal. It involves not only electoral jousting over the years but the death of his twin brother.

How the latest chapter plays out will shape the path of a country that’s clashed repeatedly with its fellow European Union states and now risks upending three decades of harmony with its biggest ally across the Atlantic after Washington slammed a new media law that threatens a U.S.-owned broadcaster. 

Kaczynski is striving to keep his grip on power in the face of a weakened governing coalition and the prospect of a resurgent opposition under Tusk. Elections aren’t due until late 2023, but the loss of support from a smaller party over the media law has left his Law & Justice party with a minority in parliament and more reliant on anti-EU forces.

Meanwhile, opinion polls show Tusk’s Civic Platform jumped about 10 percentage points since his comeback, to about 25%, enough to win back power if it joins forces with other opposition groups. Law & Justice has slipped to 33%.

That makes it more critical to control the narrative, according to former Polish President Bronislaw Komorowski. Among the ruling party, the disparaging name for the news channel at the heart of the dispute with the U.S. is “Tusk Vision.” Relations with the U.S. would be collateral damage in the domestic conflict.  

QuicktakeWhy Poland’s Media Law Is Stirring Up Protest

“Kaczynski is sensing the end of his rule may be approaching,” said Komorowski, who served from 2010 to 2015 when Tusk was in power and was his party’s pick for head of state. “He wants to strengthen his position by gagging the independent media, regardless of whether he will seek to hold early elections next year or wait out the parliamentary term.”

The media law heads to the Senate next week after it was passed by the lower house on Aug. 11. It’s aimed at preventing the takeover of Polish broadcasters by Russian or Chinese companies and is similar to rules in other EU countries, the government says. It would force Discovery Inc. to sell the largest private television network, which includes the independent TVN24 news station.  

While Kaczynski and his hand-picked prime minister, Mateusz Morawiecki, have so far refused to blink, there’s still a chance the bill will be revised or withdrawn.

President Andrzej Duda—a ruling party loyalist—said on Aug. 25 that the situation is “quite special and our interests must be weighed.” Duda will have the final say after both houses of parliament finish work on the bill. The U.S. has also objected to legislation related to the restitution of property for the families of Holocaust victims.

Law & Justice accuses TVN24 of bias toward Tusk, while it’s also aired stories of sleaze and graft at various levels of government. State-owned television depicts the former European Council president as a puppet of Germany unwanted by the EU and forced to return to Polish politics. “Tusk reactivates Civic Platform with money from Berlin,” read one recent headline.

Kaczynski and his party feel their political position is threatened, said Timothy Garton Ash, professor of European Studies at Oxford University and author of books on modern Polish history. “For that very reason, they are going to these extreme lengths to defy even Washington,” he said. “Frankly, there is a kind of madness to it.”

It all goes back to 2007, when Law & Justice was in power and triggered a snap election. Kaczynski lost badly in a televised debate against Tusk, who stumped the then-prime minister about the price of basic food items and questioned his ability to connect with regular people from the backseat of his limousine.  

Law & Justice lost and was relegated to the opposition for the next two terms, while Kaczynski closely advised his twin brother, Lech, who was Poland’s president. Then came the tragedy that’s dominated Poland over the past decade. Kaczynski blames Tusk for the death of Lech in the 2010 plane crash that killed 96 people during an official visit to western Russia. Tusk was prime minister at the time.

Kaczynski and his supporters nurtured a cult of conspiracy around the crash, which independent investigators ruled was the result of pilot error during landing in heavy fog near the airstrip in Smolensk. It helped win over an electorate growing more disillusioned over wealth inequalities, leading to Law & Justice sweeping to power in 2015.

Read More: The Plane Crash That Helped One Man Take Over a Nation

The personal pain was never far away. During a tense debate in 2017, Kaczynski screamed at Tusk’s allies in parliament: “You destroyed him, murdered him,” he shouted. “You’re scumbags.”

“The trauma has been awakened and reinforced by Tusk’s return,” said Michal Krzymowski, a journalist and author of  book “Kaczynski’s Secrets” published in 2015.

In some ways, the two men are the perfect foils for each other anyway. They represent two different Polands.

Kaczynski, 72, is a stout lifelong bachelor who famously never gained a driver’s license and, until recently, his own bank account. He’s focused on righting Poland’s historical grievances and asserting its Catholic identity. He rarely travels to foreign countries and speaks only Polish.

Tusk, 64, is a European statesman who helped navigate the U.K.’s departure from the EU and is now promising to mend political divisions while focusing on issues more resonant with youth, such as the climate.

“It’s hard to imagine two people contrasting with each other more these days: Tusk as the embodiment of the EU against Kaczynski undoubtedly an EU-sceptic,” said Ewa Marciniak, a political scientist at Warsaw University.

Indeed, the Polish leadership has been castigated by the EU over everything from taking in refugees to the independence of the judiciary and gay rights. Along with Hungary, Brussels is threatening to withhold funds from Poland over their eroding of democratic standards.

After quitting as prime minister in 2014 to take up the reins in Brussels, Tusk warned of dark forces at home in Poland. On his return in July, he denounced the “evil” Law & Justice government. “I know many Poles are waiting for this nightmare to be over,” he said.

The renewed duel is set to determine if Poland will complete its transition from one of the West’s greatest success stories following the Cold War to one of the EU’s biggest renegades, and now at loggerheads with the U.S.

Since the fall of communism in 1989, Warsaw has viewed the U.S. as the best deterrent against the unwanted influence of Russia. The greater issue now is that Law & Justice appears willing to isolate Poland, said Timothy Snyder, history professor at Yale University. The aim, he said, is simply to “ensure that the people who currently run Poland stay in power indefinitely.”

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