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's elections are taking place on Sunday, and it is the party set to finish second that is attracting much of the attention. The far-right AfD could win as many as 145 of the Bundestag's 630 seats, according to polling. This comes just 12 years after the party was founded.

On a wet evening in Suhl, in the former East Germany, a smattering of youthful faces were among hundreds lining up to hear from an unlikely idol - Björn Höcke, one of the most controversial figures in the far-right Alternative for Germany (AfD) party.

Germans will head to the polls Sunday looking for leadership at a deeply uncertain time, but all eyes will be trained on a party likely to finish a distant second.