Between 2018 and 2021, he served as Head of the Chancellery and Federal Minister for Special Affairs in the fourth coalition government of Chancellor Angela Merkel.

Braun, who was thought of as a party insider, loyal to moderate Merkel, ran in the December 2021 CDU leadership election, but only came in a distant third.

From 2001 until 2009, he was a scientific assistant at the Clinic for Anaesthesiology, Intensive Care and Analgesic Therapy of the University Hospital of Giessen and Marburg.

In Merkel's second coalition government, Braun was Parliamentary Secretary of State for Education and Research,[3] serving alongside Thomas Rachel under successive ministers Annette Schavan (2009–2013) and Johanna Wanka (2013).

Merkel subsequently appointed him as Parliamentary Secretary of State for Bureaucracy Reduction and Federal-State Relations,[5] serving directly under her in the Federal Chancellery.

[6] After the 2017 elections and the successful coalition talks between the CDU/CSU and SPD in February 2018, Braun became the designated Head of the Chancellery and Federal Minister of Special Affairs in the fourth Merkel government.

[citation needed] In April 2023, Braun was one of the 22 guests at the ceremony in which Angela Merkel was decorated with the Grand Cross of the Order of Merit for special achievement by President Frank-Walter Steinmeier at Schloss Bellevue in Berlin.