In 2017, Koike launched and led a new national political party. It was called Kibō no Tō, which means "Party of Hope". Although still Governor of Tokyo, she was the primary leader of this party. It was assumed that this party could have been the main opposition to the LDP. On October 22, 2017, the Party of Hope did not perform as well at the polls as expected. Koike's overarching policies were similar to those of Prime Minister Shinzo Abe. The policy to set them apart was their differing opinions on nuclear energy. Koike was opposed to it as an advocate of the environment. Koike did not join any successor party to the Party of Hope at its April 2018 dissolution.