Polls point to heavy defeat for Merkel's Christian Democrats which means the Social Democrats may be able to ditch them from their coalition
German Chancellor Angela Merkel's Christian Democrats are bracing for a second loss as Berlin city votes on Sunday.
Voters are expected to express their unease about Merkel's open-door migrant policy in today's vote.
Merkel's decision to open Germany's borders to refugees a year ago has boosted support for the anti-immigrant Alternative for Germany (AfD) party. AfD has played on voters' fear of the migrants, winning nine of Germany's 16 states. There have been concerns about the cost of letting the migrants in and their integration.
AfD's Berlin candidate Georg Pazderski told Reuters: "I favour educating these people (immigrants) but not integrating them. We must prepare them for going back."
Polls point to heavy losses for Merkel's Christian Democrats (CDU) in the vote which means the centre-left Social Democrats (SPD) may be able to ditch them from their current coalition, Reuters reported.
With only a year left until the next federal election, Merkel's refugee-friendly policy has dented her popularity.
Merkel has defended her policy, appealing to Berlin's openness. "Berlin, its whole history, the success of what was West Berlin, its openness has served it well and must be preserved," Rueters quoted her as saying.
Merkel's conservative allies in Bavaria have called on her to toughen up the migrant policy with measures such as capping the number of refugees to 200,000 per year.
The recent election reversals have even raised questions about whether Merkel will stand for a fourth term next year.
An INSA poll this week put the CDU to win 18 per cent of votes in Berlin, down by more than five points from the 2011 vote and only four points ahead of the AfD.
Carsten Koschmieder, political scientist at Berlin's Free University, predicted further damaging splits between the CDU and CSU if voters reject conservatives in Berlin.
"Critics of Merkel will get louder while her supporters in the CDU will blame (CSU leader) Horst Seehofer for using destructive rhetoric," he told Reuters.
Voting in the German capital started at 8 am (0600 GMT) and some 2.5 million people are eligible to decide who should represent them in the Berlin city assembly.
Polling stations will close at 6 pm (1600 GMT) and public broadcasters will publish exit polls shortly afterwards. First projections are expected roughly half an hour later.
(WION with inputs from Reuters)