On 5 June 2018, after the successful motion of no confidence on Mariano Rajoy, and the later's removal from the post of Prime Minister and his decision to also resign as leader of the People's Party, Sáenz de Santamaría postulated herself as candidate in the upcoming primaries to elect a new party leader. Soraya Saénz de Santamaría edged the 1st position in the voting held among party members with a narrow margin of 1,500 votes over Pablo Casado, with otherwise staunch rival María Dolores de Cospedal coming in 3rd. On July 21, 2018, a run-off (now voted among party delegates) between the first and second candidates in the first round was held between her and Casado. Sáenz de Santamaría lost to Casado, who became the new party leader, in what was considered a party swing towards the right. Some months following her defeat, in September 2018, Sáenz de Santamaría announced that she was leaving politics after 18 years.