She had been a lawmaker of the National Diet from 1992 to 2016 when she quit the Diet lawmaker position and ran for the Tokyo gubernatorial election. Before her, two successive Tokyo Governors were forced to resign in the middle for their terms for various scandals. She created a boom and wan the election.
During her 24-year terms of a Diet lawmaker, she changed parties she belonged to several times. She was a member of the Liberal Democratic Party (LDP) when she decided to run for the Tokyo gubernatorial election last year. The president of LDP is Prime Minister Shinzo Abe. However, PM Abe in his cabinets since 2012 never appointed her to a Minister of State although she had been appointed to the Minister of Defense in Abe's cabinet when he was previously prime minister of Japan from 2006 to 2007. The relation between PM Abe and Ms. Koike was not good. So, last year, while LDP led by PM Abe supported another candidate for Tokyo Governor, Ms. Koike dared to run for the Tokyo gubernatorial election, challenging PM Abe's leadership. She even established Tomin First party for election of Tokyo metropolitan assembly election this summer. Tomin First party got more seats than LDP got. It looked as if Ms. Koike had defeated LDP and PM Abe.
In this lower-house election, Ms. Koike has established the Kibono-to party and sent about 200 or more candidates. As she is conservative, which is proved by her former membership in LDP, two conservative parties are facing each other: LDP led by PM Abe and Kibono-to led by Ms. Koike. Kibono-to took in many conservative members of Minshin-to, the largest opposition party till the lower-house dissolution at the end of this September. She made them consent to accept conservative plocies she drafted. The liberal or leftist members of Minshin-to who could not accept the conservative policies launched their won new party, the Constitutional Democratic Party of Japan. So, Minshin-to was virtually split into two new parties: Kibono-to and the Constitutional Democratic Party of Japan.
LDP had more than 280 seats and Minshin-to had about 90 seats in the lower-house before the dissolution. In this election, the majority is 233. PM Abe aims to secure 233 or more seats in a tie up with Komei-to that had 35 seats before the dissolution of the lower house. But the approval rate of PM Abe has decreased to less than 40% recently. Ms. Koike's Kibono-to is expected to win around 150 seats. So, although it is not estimated that PM Abe and LDP/Komei-to would lose a majority, Ms. Koime's Kibono-to will be the largest opposition party.
However, Ms. Koike will reportedly not run for the lower house election. She will continue to be Tokyo Governor. But she is the head of Kibono-to. After the election, the lower house will vote for the prime minister. The problem is who the Kobono-to's lower house lawmakers will vote for as prime minister. They cannot cast votes for Ms. Koike, since she is Tokyo Governor. However, some people suspect that she will run for the lower-house election immediately before the official campaign period that will start on October 10 during which no other candidates can announce their candidacy.
The Japanese Media is reporting on Ms. Koike more often than PM Abe nowadays. Indeed, Tokyo Governor Koike is the most focused on in this lower house election in Japan.