Speaking after talks with party grandees in Berlin, Kramp-Karrenbauer said they had agreed to hold an extraordinary congress to elect the next leader of the CDU, a party that has dominated politics in Germany for 70 years. The winner is then also expected to be the CDU's candidate for the chancellery in a general election set for 2021, when Merkel plans to bow out after her fourth term at the helm of Europe's top economy.
Kramp-Karrenbauer, widely known as "AKK", told reporters the leadership vote would send "a very clear signal", adding: "It answers the question of who will be the CDU's candidate for the chancellery."
For the first time, AKK also named the four party members expected to throw their hat in the ring, confirming widespread media speculation. They include Merkel's longtime rival Friedrich Merz, popular with the CDU's more conservative factions, and the centrist state premier of North Rhine-Westphalia Armin Laschet.
Merz, who narrowly lost to Kramp-Karrenbauer in 2018's party leadership vote, is expected to announce his bid for the CDU's top post at a press conference on Tuesday. Monday's top-level talks in Berlin came a day after the CDU suffered its second-worst result ever in a regional election, coming third in Hamburg with just 11.5 percent of the vote.
The party is also engulfed in an internal debate as to how it should position itself against the extremes of right and left that have reshaped Germany's political landscape.
After barely a year as head of the party, AKK announced her resignation on February 10 after regional lawmakers in the eastern state of Thuringia voted with the far-right Alternative for Germany (AfD), defying an edict from Berlin not to ally with the extremes.
It was another sign that the defence minister had failed to stamp her authority on the CDU and become a credible candidate to succeed Merkel, who according to polls is still Germany's most popular politician. But AKK's downfall also laid bare the challenge for her potential successor: how to make their mark while Merkel remains chancellor.
"The CDU is a party in the stranglehold of a lame-duck leader," the Bild newspaper wrote. The next chancellor candidate "must first of all pull the CDU back from the abyss, otherwise they can forget about winning the next election", it added.
In the starting blocks are two politicians who promise to break with Merkel's centrist course and lead the CDU rightwards, in a bid to win back voters from AfD. While the pro-business Merz recently described her fourth government as "abysmal", young Health Minister Jens Spahn is a rising party star.
Facing them are two centrist candidates: Merkel loyalist Laschet, who wants Germany to take a leading role in closer EU integration and Norbert Roettgen, a former environment minister dismissed by Merkel in 2012. The choice of leader will set the tone for the future of the party as polls highlight the urgent need for action, with only 27 percent saying they would back the CDU, ahead of 23 percent for the Greens and 14 percent for the far right.
Beyond the high-profile personalities, the conservatives also need to clarify what they stand for in an increasingly splintered political landscape that hinders stable majorities, be it in Berlin or the 16 state parliaments. Top of the list is whether the CDU will stick to its rigid policy of refusing to cooperate with either the far right or the far left, an increasingly difficult position to maintain.
Thuringia is a textbook case, as last year's regional elections produced no clear governing majority following a surge by the AfD. CDU state lawmakers voted with the far right, breaching a historic political taboo, to install a liberal state premier.