But the main public opposition to the project has come from the larger Freedom Party, which has a strong base in Carinthia, and whose former leader Jörg Haider was once the state’s governor. Mr. Haider, who died in a car accident in 2008, was a flamboyant and media-savvy leader who brought anti-immigrant and anti-European Union views into the mainstream in Austria.

The stakes are high for the Freedom Party in Sunday’s election. Support in Carinthia, its former bastion, has slumped; in regional elections in 2018, it secured less than a quarter of the vote. Austria’s last coalition government was brought down in May after a video emerged showing Heinz-Christian Strache, the party’s current leader and the country’s vice chancellor at the time, promising government contracts in exchange for financial support from a woman he thought was a wealthy Russian.

Peter Kaiser, Carinthia’s current governor and a member of the center-left Social Democratic Party, said in a telephone interview that he did not think the attacks on the project had been successful. “Day by day, we’ve seen between 3,000 and 7,000 spectators,” at the stadium, he said.

The protesters, he added, were “just attacking it and hoping people who have an opposition to the climate situation, have an opposition to green policy, have an opposition to art, vote for them.”

Gernot Darmann, the Freedom Party’s chairman in Carinthia, denied the party opposed the installation because of its environmental message. In fact, he said in an email, “The project leaves a devastating ecological footprint,” because the trees were imported.