Federal Chancellor Friedrich Merz (CDU) attends a Bundestag session in Berlin. AP
"There is more at stake than just the future of a government" in the elections in Saxony-Anhalt and Mecklenburg-Western Pomerania, he said in a speech to his party congress in the latter region.
The far-right Alternative for Germany (AfD) is well ahead in these former East German states and polls have shown it overtaking Merz's centre-right alliance at national level, prompting talk of his potential ousting.
"If we are not good enough, then just such a big bang will happen" in September, "in a different way from what some may have imagined," he said.
Merz is the most unpopular leader of post-war Germany, struggling to pass economic reforms with the centre-left.
A new poll by the Insa Institute published on Saturday in the newspaper Bild showed his CDU/CSU alliance down to 21 percent of voting intentions against 29 percent for the AfD -- the centre-right's worst rating since 2021.
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