During her campaign to succeed Merkel as party leader, she repeatedly noted that she was able to blunt an onslaught by the anti-immigrant Alternative for Germany (AfD) party as it picked up seats in state after state.
Chancellor Angela Merkel's party is meeting Friday to elect a new leader who could help shape Germany's political direction for the next generation.
The third candidate, health minister Jens Spahn, appears to have less chance of winning.
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"We kept a cool head", she said.
Whoever wins will face towering challenges for the party, which is now drawing roughly 30% at the polls, far below the around 40% it enjoyed during Merkel's heyday. What she has said about the Merkel era became something of a slogan for her candidacy: "One cannot arbitrarily continue in the same vein, neither can one dismiss it".
After being nominated by Chancellor Merkel, AKK was elected as CDU general secretary with a record 98.9% of the vote.
She reminded the CDU of other electoral successes last year, avoiding mention of this year's setbacks in state elections, which were heavy blows for her.
While Kramp-Karrenbauer, 56, is viewed as similar to Merkel with an even temper and middle-of-the-road policies, Merz, 63, has become the torchbearer for those seeking a more decisive break from the chancellor.
While she has called for tougher policies on refugees who commit crimes, AKK firmly backed Merkel's fateful 2015 decision to welcome more than one million asylum-seekers from crisis zones such as Syria and Iraq.
Delegates hold a cardboards reading: "Thank you chief for 18 years as CDU chairwoman" during Christian Democratic Union (CDU) party congress in Hamburg, Germany, December 7, 2018.
While Merkel remains popular, AKK inherits a diminished party which is now polling at roughly 30 percent, far below the about 40 percent enjoyed during Merkel's heyday.
Merkel, however, recalled that the CDU was in a deep crisis when she took over in 2000, mired in a party financing scandal surrounding ex-Chancellor Helmut Kohl.
They were said to be reasonably close, and the lack of communication between the two raised eyebrows at the time.
"We can't afford another year like 2018 when we fought so much", he told public broadcaster ZDF.
Merkel appealed to the party to show unity, noting that arguments in recent years over migration have showed "where endless arguments lead".
'I wasn't born as chancellor or as party leader, ' she said.
The party has long languished in Merkel's shadow and could well decide to jump ship before 2021 to seek to avert further vote debacles - a move that would nearly certainly trigger new elections.
She was given a 10-minute standing ovation with cries of "Danke Angie" to acknowledge her 18 years in the job.