In April 2006, Mayor Ole von Beust appointed him as state councilor of the Department of Sport and Home Affairs.

[5] On 7 May 2008, Ahlhaus replaced Udo Nagel and became the Home affairs senator of the Free and Hanseatic City of Hamburg.

[9] Ahlhaus continued despite tight budgets in 2010 through the acquisition of a riding squad with a total investment of approximately €600,000 and annual operating costs of €200,000.

[11] His desire to hold on to the continued existence of the police orchestra, with an annual cost of 1.5 million euros, was in some part because of a lack of understanding, despite his cuts in the cultural department.

His recommendation to nominate Christoph Ahlhaus as his successor was unanimously followed by Hamburg's CDU Regional Executive.

The election of the First Mayor of the CDU-Green Senate majority was fixed for the first meeting of the citizenry after the parliamentary summer recess on 25 August 2010.

Ahlhaus put himself firmly behind the agreement between the CDU and GAL, which had existed since 2008, and also expressed his readiness to face the Green base in August 2010.

This triggered anger in the GAL, and leaders of the party put the support of their faction in the election for the Lord Mayor in question.

They demanded Ahlhaus' clarification about his relations with the Turnerschaft and complained that in their view, nationalist tendencies and misogynistic principles are present in connections with the Coburg Convents.