Attendees overflowed the original venue at the Hotel Intercontinental, causing the Alternative for Germany party to book an additional conference room, the EUObserver reported Monday.
"There is something like a free speech police here in Germany saying there is no alternative to the euro," said party co-founder Konrad Adam in the opening speech. "We are the alternative now."
A poll published Friday by broadcaster ZDF found 17 percent of German voters say they could vote for a party that favored exiting the euro.
To have a seat in the Bundestag, or parliament, in the Sept. 22 elections, Alternative for Germany would have to receive at least 5 percent of the vote. While pollsters consider that unlikely, any success by the new party could imperil the Liberals, who are at 4 percent in the polls and coalition partners with Chancellor Angela Merkel.
Some 66 percent of Germans consider exiting the euro would be "rather bad" for the country, while 26 percent say it would be a positive step, the ZDF poll reported.
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