BERLIN — Chancellor Angela Merkel faces a voter backlash in elections Sunday over her open-door policy that has allowed a flood of migrants to settle in Germany.

The vote in three German states is the first electoral test for Merkel, 61, before national parliamentary elections next year.

The chancellor allowed more than 1 million migrants fleeing wars and poverty to enter Europe's largest economy to apply for asylum, a move that has put her at odds with many members of her conservative Christian Democratic Union (CDU) party and alienated large swathes of the German public.

The parliamentary elections in Baden-Württemberg, Rhineland-Palatinate andSaxony-Anhalt have been labeled "Super Sunday," a nod to the "Super Tuesday" presidential primary elections and caucuses in the United States this month.

More than 12 million of Germany's 62 million eligible voters may cast ballots. The last public opinion polls before the vote showed a surge in support for Alternative for Deutschland (AfD), a populist, anti-immigrant party. It shocked Germans earlier this year when its leader Frauke Petry, 40, said police may need to shoot migrants at the border.