Supporters of the hard-right Alternative for Germany (AfD) party shout slogans during an election campaign rally for German Chancellor Angela Merkel in Torgau, Germany, on Sept. 6. (Reinhard Krause/Reuters)

BERLIN — The campaign of a far-right German party poised to topple a postwar barrier and enter Parliament for the first time is premised on persuading voters that they are not alone in supporting the faction, Alternative for Germany, or AfD.

The party's most useful ally in this effort is the Internet, that vast space connecting people across space and time to others who think just like them. The capacity to light up the Web with far-right talking points has played no small part in positioning the party to possibly place third Sunday with 11 to 13 percent of the vote, according to the most recent polling.

That the AfD relies on Facebook, Twitter and Google — companies that have been drawn into the high-stakes debate over Russian interference in the U.S. election — casts further light on the global dimensions of the struggle to sort out the responsibility of tech giants and the bounds of political speech. Facebook reversed itself Thursday and agreed to give Congress copies of thousands of political advertisements purchased through Russian accounts during the U.S. presidential campaign last year.

The campaign in Germany has unfolded without substantial evidence of the sort of Russian meddling that, officials say, marked recent elections in the United States and France, countries subject to phishing attempts and “fake news” in the days and weeks before voters went to the polls. This has generated concern that the Kremlin has opted for other means of interference, including efforts to undermine the voting process itself.

With or without the help of Russian hackers, however, the AfD has made online advertising and Web messaging focal points of its strategy. It enlisted Harris Media, a Texas-based agency with ties to President Trump, to hone its communications in the final weeks of the campaign.

“The AfD has been more prominently doing work on social media than any other party in Germany,” said Karolin Schwarz, a fact-checker with correctiv.org, a nonprofit research center that has been monitoring online extremism ahead of Sunday's election.

Digital platforms are free of the obstacles that have frustrated more traditional campaigning undertaken by the nationalist, anti-immigrant party.

Its rallies are magnets for protesters; especially in the big cities, many of their posters have been torn down. The party faces difficulty booking space in restaurants and other private venues.

Its leadership has deep distrust for the German media, leading the party to prefer “the echo chambers of the Internet,” said Werner J. Patzelt, an expert on right-wing extremism at the Technical University of Dresden.

“In this sense it is the most modern campaign of them all,” Patzelt said. “The AfD has harnessed the Internet as a modern marketplace, where they have given voice to the idea that the political elite of Germany has guided the country in the wrong direction.”

Even the Internet, however, is not a neutral space for its ideas, party operatives are alleging. Part of what Harris Media, the U.S. firm, offered were ties to Silicon Valley, allowing the party to bypass German subsidiaries of companies such as Google and Facebook.

But Thor Kunkel, the AfD's campaign manager, told Spiegel Online that Google had sabotaged a website it had produced attacking Germany's chancellor, Angela Merkel, who is poised to claim a fourth term.

Featuring a grim image of Merkel imposed over Berlin's Kaiser Wilhelm Memorial Church, where a failed asylum seeker killed 12 people with a truck last year, the website has scant identification linking it to the AfD and was for a time a top result for queries with the chancellor's name.

According to Spiegel, there was an extensive email correspondence between a Google team and AfD officials in which the California-based company offered shifting justifications for impeding the advertisement.

The site is live, and Google denies politically motivated interference.

“Every political party that is listed in Germany can advertise on Google as long as it follows our policies and any claim of political bias is baseless,” Chi Hea Cho, a spokeswoman, said in a statement. “We enforce our policies ​​vigorously, all ads go through an automated approval process and we may look into borderline cases more extensively.”

Germany enforces strict hate-speech laws, a cornerstone of de-Nazification, but the question now, said Patzelt, the political scientist in Dresden, is whether Internet companies should censor material that might toe that line — and escape the immediate attention of the government.

“My feeling is as long as there's no preparation for a political crime but just opinions we dislike, it's important not to restrict political freedom,” he said.

But Maksymilian Czuperski, director of the Atlantic Council’s Digital Forensic Research Lab, said the issue is not merely whether something is offensive but whether it's rooted in reality. The AfD, he said, relies on manipulation and, in some cases, traffics in blatantly false information.

An image recently shared by a regional chapter of the party, evoking mass sexual assaults in Germany on New Year's Eve in 2015 and calling on people to vote, was doctored, its origins linked to a white-supremacist and anti-Semitic site, Czuperski said.

The image has been a favorite of AfD-related accounts nonetheless, gaining added publicity through “bots and fake accounts, both alt-right and pro-Russian,” Czuperski said.

He said these accounts are not as active as they were during the French or U.S. elections. Yet there are other means of influence, he said, including the distribution of AfD material on VKontakte, or VK, a Russia-based social-media platform.

There is also concern that the apparent absence of concerted Russian activity masks new tactics.

“It's worth asking yourself why it's so quiet,” Czuperski said. “The objective of interference from what we've seen is not support for one candidate or another but to undermine the electoral process. That can be achieved in other ways than fake news.”

Election day may be a critical moment, he said, particularly given discussion in corners of the Internet sympathetic to the AfD about going to polling places to observe the vote.

“There is already chatter on some accounts about the election being rigged, which is dangerous,” he said.