While Mrs Merkel has not explicitly endorsed any of the three candidates, Kramp-Karrenbauer is largely seen as her favourite having been brought into federal politics earlier this year in February when Merkel appointed her General Secretary of the party. However, it's possible elections could be called before then.
A lot of them defected to the far-right Alternative for Germany over Merkel's controversial decision to openly welcome asylum seekers back in 2015 when hundreds of thousands of Syrians, Iraqis, Afghans and others came to Germany and other European Union countries to escape war and poverty.
One of the most recent examples of Merz wanting a change of course for the CDU has been his outspoken criticism of the United Nations migration pact, which was revealed to have been largely drafted by the Merkel government starting in 2016.
German Chancellor Angela Merkel on Friday, December 7, offered a staunch defense of her moderate course during 18 years as party leader, as her Christian Democratic Union chose between a loyal deputy and a longtime rival to succeed her. She defeated Friedrich Merz in the second round of voting after Health Minister Jens Spahn was eliminated.
She joined the CDU in 1981 as a 19-year-old student and, after completing a masters in political science, worked in state-level politics.
Kramp-Karrenbauer was the first woman to be a German state's interior minister, or top security official, and served as the governor of western Saarland state, defying expectations to win re-election by a wide margin past year.
AKK is the new leader of Germany's CDU party - but won't immediately become the new Chancellor of Germany.
By contrast, Merz takes clear positions that appeal to rank-and-file party members hungry for a more clearly defined party after 13 years under Merkel as chancellor.
Economy Minister Peter Altmaier, a close Merkel ally, criticised Schaeuble's vocal support for Merz as divisive and threw his weight behind AKK as a moderate force who can keep voters from drifting to the extremes. She also allowed the introduction of gay marriage, which Kramp-Karrenbauer was more vehement in opposing. She would be the most unsafe candidate to face the center-left Social Democrats and the ecologist Greens, he added.
Merkel listed some of those moments and many more in a half-hour farewell speech as leader, telling delegates that 'our CDU today is different from the year 2000, and that is a good thing'.
At present, the center-right bloc is polling around or below 30 percent. Merkel's fourth-term governing coalition with the center-left Social Democrats has lurched through a series of crises since taking office in March, and the CDU has lost supporters both to the liberal Greens and the far-right Alternative for Germany.
"This is democratic order, which reflects a self-confident party", she said. "But. we faced an hour of destiny for the Christian Democratic Union 18 years ago".
"The election of AKK as leader of the CDU is an indication of the continuing strength of Angela Merkel in her party". She said that "we kept a cool head" and "we showed everyone" by recovering. "I have always wanted to do my government and party jobs with dignity, and one day to leave them with dignity. now it is time to open a new chapter".
Waving orange cards with the slogan "Thank you boss", delegates cheered as Merkel, 64, walked onto the stage at the conference centre in Hamburg, her birthplace, to end an era for the party.