Mr. Merz needed two rounds of voting to become chancellor after a surprising defeat in Parliament hours earlier that threatened to hobble his new government.

In a historic first, conservative leader Friedrich Merz ’s bid to become Germany’s 10th chancellor since World War II failed in the first round of voting in parliament on Tuesday by six votes, a stunning defeat as he had been widely expected to win smoothly.

It was the first time in Germany’s postwar history that a chancellor-designate has failed to win an absolute majority.