Simmers was sworn in as a Member of the
Western Cape Provincial Parliament on 12 June 2017. On 7 November 2020, Simmers was elected unopposed as chairperson of the DA's east region in the Western Cape. He took over from
Jaco Londt, who stood down. Simmers was a candidate for DA deputy provincial leader, but lost to incumbent
Albert Fritz at the DA's provincial elective conference on 21 November 2020. On 15 April 2021, Simmers was appointed as the acting Provincial Minister of Transport and Public Works following the suspension of
Bonginkosi Madikizela, who was also the provincial leader of the DA at the time, after he was caught falsifying information on his CV. Madikizela soon resigned from the provincial government on 28 April. Simmers continued to serve as acting Provincial Minister until
Daylin Mitchell was appointed as the Provincial Minister of Transport and Public Works on 25 May. On 21 August 2021, Simmers was elected as the interim deputy provincial leader of the Democratic Alliance in the Western Cape, defeating his only opponent for the position,
Breede Valley Mayor
Antoinette Steyn. His election came after the role of deputy leader became vacant when Fritz resigned after his election as interim provincial leader following Madikizela's resignation. At the age of 38, he became the youngest ever deputy provincial leader of the party in the Western Cape. In January 2022, interim DA provincial leader
Albert Fritz stepped aside from the position amid a sexual misconduct scandal. Simmers was appointed as the acting provincial leader for the time being. Fritz officially resigned from the position and the DA on 1 March 2022 after an independent report found sufficient evidence of sexual misconduct. On 18 April 2022, the DA announced that Simmers was the only candidate nominated for interim provincial leader ahead of the party's provincial council meeting on 7 May 2022. On 7 May 2022, Simmers was elected unopposed as the DA interim provincial leader. At the DA's provincial conference on 11 November 2023, Simmers was elected DA provincial leader for a full term, having defeated former provincial leader
Bonginkosi Madikizela. After
Alan Winde was re-elected for a second term as premier on 13 June 2024, he announced his provincial cabinet for the new administration which saw Simmers remain as Provincial Minister of Infrastructure. == Controversies ==