Angela Merkel could face a humiliating defeat in regional elections in her own constituency of Mecklenburg-Vorpommern, where some polls have put her Christian Democratic Union party third behind the Social Democrats and the rightwing populists Alternative für Deutschland.

Earlier this year, the chancellor’s centre-right CDU looked like the party most likely to be tasked with forming the next government after Sunday’s vote in the eastern state, but in one recent survey its support dropped to 20%, behind the AfD on 23% and the centre-left SPD on 28%.

For the past 10 years, Mecklenburg-Vorpommern has been governed in a “grand coalition” between the SPD and CDU, mirroring the current power structure at federal level.

An increasingly divisive debate over the consequences of the German government’s strategy during the refugee crisis has spurred support for the anti-immigration AfD – fronted in the state by Leif-Erik Holm, a radio presenter based in Berlin’s multicultural Prenzlauer Berg district – even though only 3.7% of the state’s population is of non-German background, one of the lowest rates in the country.

Facebook Twitter Pinterest Leif-Erik Holm of Alternative für Deutschland (AfD) . Photograph: Joachim Herrmann/Reuters

In May, a pig’s head carrying an insulting message was left outside Merkel’s constituency office in the Baltic sea town of Stralsund, where the German chancellor has won a direct mandate since 1990.

The northernmost of the five former East German states that joined with the West German federal republic in 1990, Mecklenburg-Vorpommern has in the past been troubled by industrial decline and a dwindling population, but last year registered the lowest unemployment rate and highest GDP since reunification.

In part due to its economic weakness and low population density, the region was assigned fewer refugees than all but two of Germany’s 16 other Länder; 23,080 asylum seekers were registered in Mecklenburg-Vorpommern in 2015, roughly a quarter of those assigned to similarly sized Hesse.

In the past year, the state has registered no high-profile criminal incidents, such as terrorist attacks or rape, carried out by asylum seekers, and a decline in theft and violent crime. Police in Mecklenburg-Vorpommern recorded seven incidents of attempted arson at refugee shelters in 2015.

A shooting rampage in Munich and two attacks with an Islamist motive in regional towns in Bavaria in July have fostered a national debate about internal security. Lorenz Caffier, the Christian Democrat candidate in Mecklenburg-Vorpommern, was one of the politicians behind a call for a ban on the full face veil in Germany last month.

Polls in the region close at 6pm local time (5pm BST) on Sunday, with first exit polls expected to be announced an hour later.