Kramp-Karrenbauer appears to be Merkel's preferred successor, which hasn't surprised her party companions who have for months referred to her as "Mini-Merkel".
As Merkel's power within her own party is fading, being so closely associated with the Chancellor could still disrupt Kramp-Karrenbauer's plans to take over as party leader.
Kramp-Karrenbauer is eight years younger than Merkel and - just like Merkel - stands for the party's moderate wing.
Kramp-Karrenbauer became minister-president of the federal state of Saarland in 2011 and remained in power until this year, when she was named the CDU's general secretary. Her appointment has always made her a likely contender in any future leadership vote.
A possible failure of Merkel to install Kramp-Karrenbauer as her successor would be seen as yet another defeat for the Chancellor.
Jens Spahn
The 38-year old politician represents the party's right-wing faction and has sought to position himself as a possible Merkel successor for some time.
Spahn announced that he was ready to succeed Merkel as party leader today, multiple German media outlets reported.
His supporters argue that Spahn's appointment as party leader would mark a generational change and a true end of the Merkel era, which critics have associated with a lack of inner-party discourse and an embrace of issues traditionally more associated with liberal or left-wing parties.
Under Merkel, the CDU adopted or accepted liberal positions on immigration, same-sex marriage and phasing out nuclear power plants - even though some of those stances were later reversed.
A Spahn appointment would likely result in a right-wing turn of the CDU. But it would also be seen as an affront against Merkel.
Merkel loyalists would be unlikely to vote for Spahn, who would have to compete with other Merkel critics for the remaining votes.
Friedrich Merz
The 62-year-old lawyer was not necessarily a top contender as a Merkel successor but was widely discussed as a potential replacement after he put himself forward shortly after the chancellor announced she was ready to hand over the leadership position.
Merz used to be the head of the conservative parliamentary group, but he has never held a ministerial office.
Merz was forced out of his leadership position in 2002 after Merkel rose to power, which disgruntled a number of his allies at the time.
The former leading conservative left politics about a decade ago to work as a lawyer and board member of multiple financial enterprises and banks.
Armin Laschet
The 57-year-old minister-president of the federal state of North Rhine-Westphalia is frequently put forward as a possible Merkel replacement by his allies, even though Laschet has refrained from making such suggestions himself.
It is unclear whether he would be willing to resign as minister-president to accept a top role in Berlin.
But as the head of Germany's most populous state, Laschet has gained substantial government experience.
The leader of the CDU's frequent coalition partner, Christian Lindner, is considered to also be supportive of Laschet.
And his long-standing support for the chancellor could help him gain at least some votes of Merkel allies.
