The co-leader of the anti-immigrant Alternative for Germany (AfD) suffered an embarrassing defeat on Saturday when delegates refused to discuss her motion to shift the party into the "mainstream", putting it on course to turn further right.
The party, a pariah in German politics, has seen its support drop in recent months, and thousands turned up to protest the congress and the party's anti-immigrant stance.
Frauke Petry, the AfD's public face, shocked supporters on Wednesday by announcing that she would not lead the AfD's campaign for a Sept. 24 federal election.
She had ruffled feathers by proposing to rebrand the AfD as a party that would seek to join coalitions from 2021 elections rather than becoming a "fundamental" opposition party. All established parties refuse to work with the AfD.
Petry said she was prepared to edit the text with her arch-rival Alexander Gauland, whom she upset by naming as the key proponent of the "fundamental" opposition camp. Her foes within the party say the division laid out in her motion is artificial.
But delegates stressed the need to use the congress in Cologne to signal the AfD was united ahead of the elections after months of bitter infighting that have helped drag down its poll ratings by about one-third to 8-10 percent.
They voted against discussing Petry's motion or another proposal in which she and others said the AfD should reject "racist, anti-Semitic ... and nationalist ideologies".
Speaking after the vote, Petry said the AfD had made a "mistake" and added that those acquainted with the party since it was founded in 2013 knew that it was "exactly this lack of strategy" that was behind much of its internal strife.
"As long as the party does not indicate which direction it actually wants to go in, protagonists who can live with this non-decision a lot better than I can have to lead this election campaign," Petry said, adding that she would however do her bit to make the AfD successful.
Co-leader Joerg Meuthen gained wild applause - and a standing ovation from some - for saying the AfD would never form an alliance with the likes of Chancellor Angela Merkel, Social Democrat leader Martin Schulz or the Greens, who he said were wrecking Germany with their pro-migrant stances.
Around 10-15,000 protesters demonstrated against the AfD's meeting in Cologne, a police spokesman told broadcaster n-tv - well below initial expectations that 50,000 could turn up. Two police officers were injured and a police car was set ablaze.
Delegates also voted on Saturday in favor of having a team of national candidates for the election campaign despite Petry warning against such a strategy. The line-up is due to be decided on during the congress.
In a firebrand speech, economics professor Meuthen said Germans were increasingly "few and far between" and that without action now, "the irrevocable change of our homeland into a Muslim-dominated country is a mathematical certainty".
Many of the more than one million migrants who have arrived in Germany in the last two years are Muslims.
Meuthen said he was not xenophobic but was concerned about the extent to which migrants were changing Germany and that Germans did not want to become a minority in their own country.
He likened the country to the Titanic.
"Everybody is still in good spirits and there's a relaxed party mood above and below deck but it's almost impossible for the huge ship to make the necessary change in direction anymore," Meuthen said. "People can't or don't want to imagine a collision with an iceberg but it's already unavoidable."
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