The candidates

Friedrich Merz, 62, the back to the future candidate: Staging an unlikely comeback after retiring from politics in 2002. An economic liberal and social conservative, he introduced the concept of Leitkultur to the immigration debate, arguing there is a dominant indigenous culture which immigrants must respect. Since quitting politics he has made millions in the private sector. Endorsed by the CDU business wing and several party heavyweights from the Right, but has his time passed?

Annegret Kramp-Karrenbauer, 56, the “MiniMerkel”: It’s no secret AKK, as she is known, is Mrs Merkel’s preferred successor. The two women share a pragmatic, centrist view. But Ms Kramp-Karrenbauer is more than just a Merkel clone. A formidable campaigner, she halted the seemingly unstoppable advance of the Social Democrats (SPD) last year. Seen as socially liberal but is a committed Catholic and can be conservative on issues such as gay marriage. Likes to relax by listening to AC/DC. The favourite, but can she shake off the Merkel Mark II tag?

Jens Spahn, 38, the Next Generation: Long seen as the standardbearer of the party Right, the ambitious health minister has taken on Mrs Merkel over her migrant policy. At times he has been seen by the party establishment as going too far, but won praise for his focus on the health ministry this year. Seen as socially conservative over immigration, but is no throwback: he is openly gay and married his partner last year. Senior figures in the party are said to believe he is not ready for the leadership. Can his bid survive?