In September 2018, he succeeded Beate Meinl-Reisinger as the parliamentary leader of NEOS in Vienna.

[4] In December 2019, Wiederkehr was announced as NEOS's lead candidate for the 2020 Viennese state election.

Wiederkehr successfully brought NEOS into negotiations with the ruling Social Democratic Party afterwards, who agreed to a coalition government.

Wiederkehr was sworn in as Vice Mayor of Vienna and City Councillor for Education on 24 November.

[1] In June 2021, Wiederkehr was elected as federal deputy leader of NEOS, alongside Andrea Klambauer.