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BERLIN (Reuters) - Chancellor Angela Merkel’s conservatives suffered their second electoral blow in two weeks on Sunday, with support for her Christian Democrats (CDU) plunging to a post-reunification low in a Berlin state vote due to unease with her migrant policy.

The anti-immigrant Alternative for Germany (AfD) polled 11.5 percent, gaining from a popular backlash over Merkel’s decision a year ago to keep borders open for refugees, an exit poll by public broadcaster ARD showed. The result means the AfD will enter a 10th state assembly, out of 16 in total.

Merkel’s CDU polled 18 percent, down from 23.3 percent at the last election in 2011, with the centre-left Social Democrats (SPD) remaining the largest party on 23 percent. The SPD may now ditch the CDU from their coalition in the German capital.

The blow to the CDU came two weeks after they suffered heavy losses in the eastern state of Mecklenburg-Vorpommern. The setbacks have raised questions about whether Merkel will stand for a fourth term next year, but her party has few good alternatives so she still looks like the most likely candidate.