In January 1990, just after the Peaceful Revolution in East Germany, he moved to Erfurt and became the manager of a hairdresser's chain in Thuringia.

[3] On 5 February 2020, Kemmerich was elected to the position of minister-president in the third ballot, with the support of his FDP (being the smallest group in the state parliament) as well as lawmakers of the centre-right CDU and the far-right AfD.

On 7 February, Kemmerich met with Birgit Keller, the President of the Landtag of Thuringia, to discuss possibilities for a swift transfer of power to a new minister-president.

Kemmerich announced he would stay in office until the matter is resolved in order to secure political stability for the state.

[5][6] On 8 February, he resigned his post but stayed in office as acting minister-president until the election of a successor, as mandated by the state constitution.