The leading candidate, Friedrich Merz, a conservative who has adopted many of the AfD’s hard-line positions on immigration, used his closing statement of the debate to promise his voters that he would never allow the AfD into his government. Under him, he said, the firewall would hold.

Germany holds a national election on Sunday following an acrimonious campaign in which the far-right Alternative for Germany (AfD) challenged the country’s postwar tradition of moderate, consensual politics.