A nationalist party that wants Germany to close its borders to migrants, leave Europe's common currency and end sanctions against Russia is predicted to enter parliament for the first time this month.
The party's increase in popularity is propelled by voters' anger at German Chancellor Angela Merkel's decision to let over a million refugees into the country since 2015.
Alternative for Germany, or AfD, is forecast to take between 8% and 11% of the vote on September 24, giving it dozens of politicians in the national Parliament.
Some polls even project it could even come third behind Mrs Merkel's party and the centre-left Social Democrats.
If the predictions are correct, it would be the first time in 60 years that a party to the right of Mrs Merkel's conservative Union bloc has attracted enough votes to enter the Bundestag.
"It's quite an achievement for a right-wing party to clear the 5% minimum threshold," said Gideon Botsch, a political scientist at the University of Potsdam near Berlin.
AfD's poll numbers are all the more remarkable because the party has become increasingly extreme since its founding in 2013, he said.
"German voters haven't wanted to vote for a right-wing party in recent decades," Mr Botsch said.
"Germany's Nazi history is obviously one of the reasons for that."
At an election rally last week in the southwestern city of Pforzheim, the mostly male, middle-aged audience gave a standing ovation to party co-leader Alexander Gauland, a 76-year-old former civil servant who sparked controversy last year by saying that Germans do not want to live next to a black football player.
Mr Gauland, a former member of Mrs Merkel's Christian Democratic Union, made headlines again recently for suggesting that the government's integration tsar should be "disposed of" in Turkey, where her family emigrated from before she was born.
Mr Gauland touched on a subject the party's supporters are particularly anxious about: the influx of migrants from Muslim-majority countries such as Syria, Iraq and Afghanistan.
"Only if we defend Europe against a new Islamic invasion do we have a chance to remain a majority in this country and survive," he told the crowd.
Mr Gauland's anti-Islam comments fell on fertile ground in Pforzheim, at the northern tip of Germany's Black Forest.
His party achieved a surprise victory there in last year's regional election.
It now has seats in 13 state assemblies and the European Parliament.
Observers say AfD benefited from Pforzheim's large population of so-called Russlanddeutsche, ethnic Germans who emigrated from the former Soviet Union and hold more conservative views than the general population.