After migrant influx, voters ask: what makes a citizen?

Germans vote in a general election on Sunday after a campaign which has seen parties spar over how closely refugees and immigrants should integrate into the national culture, sparking fierce discussions about what it means to be German.

What started the debate?

The armies of Turkish "guest workers" brought over for German factories after the devastation of World War II had kept the integration debate simmering for decades.

But it was propelled to centre stage in the 1990s by university professor Bassam Tibi, himself from a migrant background.

Tibi suggested that the country needed a "Leitkultur" or "leading culture" which would transmit European Enlightenment values like democracy, tolerance and pluralism to new arrivals.

But the term was quickly embraced by rightwingers in Chancellor Angela Merkel's Christian Democratic Union (CDU) to mean an essentially German culture.

Since then, "the term is used to mean that there is something typically German, or Christian-European, that should unite a diverse population," said Alexander Schunka, a professor at the Free University of Berlin.

"No one has ever really understood the term," Tibi told the Tagesspiegel daily in July.

Why is identity back in the spotlight?

The arrival of more than a million asylum seekers since 2015, mainly from Muslim countries, has deeply divided Germany.

The AfD in particular has capitalised on anger over the influx, transforming itself from an anti-euro upstart into an anti-Islam, anti-immigration party.

Some of the party's views shade into conspiracy theories, including the "great replacement" belief that politicians plan to repopulate Europe with cheap, pliable immigrants.

And warnings that Islamic culture will overrun Germany are omnipresent in the party's messaging.

AfD campaign posters feature messages like "New Germans? We'll make them ourselves!" over a picture of a beaming pregnant white woman, or "Burkas? We prefer bikinis!" plastered across an image of nubile beachgoers.

What exactly is German culture?

The trouble with calling for a German culture to overshadow whatever migrants have brought from elsewhere is deciding who gets to define what that means.

Centuries of history as a patchwork of princedoms before unification in 1871 have left Germany with dozens of strong local cultures, cuisines and dialects.

Most of those do not conform to the beer-and-lederhosen stereotype held by many foreigners, which reflects the heritage of southern Bavaria -- as residents of the Franconia region in northern Bavaria would insist most strongly of all.

When integration commissioner Aydan Ozoguz, who has a Turkish background, recently tried to make this point, the AfD's lead candidate Alexander Gauland proposed that she be "dumped in Anatolia".

The remark implied that he saw her German citizenship as meaningless, and harked back to "the worst memories our country has left all over the world," Foreign Minister Sigmar Gabriel said.

Merkel herself had a go at defining what it means to be German in an A-to-Z article for the Bild newspaper earlier this year, in which C stood for "Christian-Jewish tradition" and M for "Muslim" and "migration background".

Bratwurst, Oktoberfest and the national football team also had a place in her Germany.

Fertile ground for the AfD?

Other politicians have also latched onto the integration theme, out of fear of losing voters to the AfD.

Interior Minister Thomas de Maiziere, of Merkel's conservative CDU party, laid out his idea of essential touchstones of German culture in a May article for Bild, emphasising "respect and tolerance", "hard work" and "enlightened patriotism".

"Social norms" like shaking hands and not covering one's face -- two endlessly debated questions about Muslim women -- were top of his list.

Meanwhile, figures on the left of the spectrum have tried to expand "Leitkultur" to a broader definition closer to Tibi's original concept.

Social Democratic politician Raed Saleh has just published a book called "German Me. The New Leitkultur", which calls for Muslims to develop their own, specifically German vision of Islam.

"Why don't we give the millions of Muslims who live in Germany a sense that they belong to society?" he told AFP.