Baillie was selected as the Conservative candidate for Stroud on 31 July 2018. Baillie supported the UK remaining within the EU in the 2016 UK EU membership referendum, but during her 2019 election campaign indicated that she now supported Brexit, to honour the result of the referendum. At the 2019 general election, she was elected as an MP with a majority of 3,840 (5.8%). The seat had been represented by David Drew (Labour) since the 2017 election. Baillie is the first woman to represent the constituency. She was appointed Parliamentary Private Secretary to the Minister of Justice in February 2020. She has been a member of the Work and Pensions Select Committee since March 2020.