CDU leader Friedrich Merz has ruled out any such alliance but caused uproar last month by bringing a motion to parliament that was passed with AfD votes, breaching a long-standing taboo.

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.

Alice Weidel, the first ever candidate of the far-right Alternative for Germany (AfD) party for the post of Chancellar, lives with her partner and two children in Switzerland.