Particular criticism has been levelled at the party's chaotic performance during the campaign for the European Elections last month, when a YouTube video attacking the party's record on climate change and income inequality went viral.
The CDU were accused of panicking after they shot their own video in response to the attack, only to axe it before publication.
Talk is already turning to whether Kramp-Karrenbauer is the best person to lead the CDU into the next election. The 56-year-old, who won a leadership election after Merkel decided to stand down as head of the party, came out fighting today, warning that the Greens were too ideologically close to Die Linke, a party of the radical Left.
"People who dream of a new Green-led government need to know that they could wake up with Die Linke in power," she told Bild am Sonntag.
Her comments came after the Greens chose to enter coalition talks with Die Linke, rather than the CDU, following elections in the state of Bremen last month.
"Bremen shows that, when in doubt, the Greens pick the left-wing over the politics of the middle ground," Kramp-Karrenbauer said.
