The September 2017 Democratic Party leadership election was held on 1 September 2017 to replace outgoing president Renhà Â, who resigned in July after the party's failure in the 2017 Tokyo prefectural election.
Seiji Maehara, the runner up in the 2016 contest, defeated Yukio Edano by a wide margin. Maehara's success was a victory for the conservative wing of the party, but also precipitated an internal crisis that resulted in a split in the party only a month later.
Renhà  was elected president in September 2016. As a younger and more vibrant face, it was hoped that she would improve the DP's poor standing, but they continued to languish in the polls and suffer from internal strife. Ahead of the July 2017 Tokyo prefectural election, more than a dozen DP candidates defected to Tomin First, significantly damaging the party. High-profile party member Akihisa Nagashima also left the party, as did Kenzo Fujisue. The DP went on to win only five seats in the Tokyo Metropolitan Assembly, down from fifteen in the previous election and their worst-ever performance. Renhà  and secretary-general Yoshihiko Noda acknowledged the defeat but gave no indication of resigning. Renhà  also continued to be pursued over claims she had failed to renounce her Taiwanese citizenship. To refute the allegations, on 18 July she disclosed part of her family register and a certificate confirming her renunciation, but pressure on her leadership remained.
At a meeting of the DP caucus on 25 July, Noda announced his resignation. Renhà  stated she would quickly appoint a successor to look ahead to the House of Representatives election, due to take place within the next year. She voiced her intention to leave the House of Councillors and seek election to a district in Tokyo in the next election. Two days later on the 27th, she announced her resignation as president: "I have decided that the best course of action is for a new executive team to lead a stronger Democratic Party. ... I also reflected on my shortcomings and took the whole picture into consideration. I lacked leadership skills."
The following day, the party executive decided that the election would use the comprehensive points-based procedure, rather than a simple caucus vote as permitted under the party statutes. On 2 August, they announced that nominations would be taken on the 21st and the election held on 1 September.
The election was conducted via a points system:
In order to win, a candidate must secure more than 50% of points. If no candidate won more than 50%, a runoff was to be held the same day. In the runoff, only Diet members and approved candidates could vote.
The election was seen as a contest between the party's conservative wing, represented by Maehara, and its liberal wing, represented by Edano. The two central issues of the campaign, electoral alliances and constitutional reform, ran through this factional divide; conflict over these issues had led to the departure of prominent conservatives Nagashima in April and then Goshi Hosono on 4 August, shortly after Renhà Â's resignation. Maehara and Edano were both prominent leaders of the party and had served in key roles over many years, including senior cabinet positions during the DPJ government of 2009âÂÂ12. Maehara previously served as president from 2005âÂÂ06 and ran for the position again in 2011 and 2016. Edano was contesting his first leadership race.
The two largest issues during the contest were electoral strategy and constitutional reform. Under Renhà Â, the party had pursued alliances with the Communist Party to improve its chances in elections, and steadfastly opposed the Liberal Democratic government's plans to amend Article 9 of the Constitution. Edano, who as secretary-general was one of the architects of these positions, pledged to continue them. Maehara opposed the alliance with the Communist Party, instead promoting cooperation with Tokyo governor Yuriko Koike, who was widely believed to have aspirations to enter national politics. Maehara was a well-known supporter of constitutional revision, though during the contest he stated his opposition to the LDP government's "hasty timetable".
Other issues included nuclear power, economic policy, and relations with Rengà Â. Edano supported the total phasing out of nuclear power and pledged to introduce a bill to the Diet to achieve this. Both candidates supported increased welfare expenditure, with Maehara prioritising support for the elderly and Edano calling for wage increases for nurses and caregivers. Both also supported free early childhood education. They differed on tax policy: Maehara proposed raising taxes to fund expanded programs, while Edano preferred cuts to public works and opposed any rise in the consumption tax. Relations with the major trade union federation Rengà Â, traditionally a major support base for the party, had also been strained due to the alliance with the Communist Party. Maehara wanted to repair ties, while Edano was seen as limited by his adherence to Renhà Â's policies.
Third-place finisher in the previous year's contest Yuichiro Tamaki initially intended to run again. However, he stated on 4 August that he would not stand, citing his responsibility for the party's recent failures in his role as deputy secretary-general. Former JIP leader Kenji Eda was urged by allies to run as a "third candidate," but chose not to do so. Yosei Ide ran, but withdrew on the 21st due to lack of support.
Maehara received support from several factions, including all those considered to lie on the party right. He was endorsed by the ex-DSP group around Yoshiaki Takaki on the 4th, followed on the 7th by Akihiro Ohata's faction, the ex-JIP group around Yorihisa Matsuno, and Maehara's own Ryounkai faction. This was followed by the former Hosono faction on the 9th and the former Nagashima faction on the 16th.
Edano was encouraged to run by Hirotaka Akamatsu and was endorsed by his faction of ex-JSP members. He was also supported by the Kan faction to which he belonged.
A 27 August poll from The Nikkei showed the general public preferred Maehara to Edano 41% to 28%. Among DP supporters, the two were tied on around 40%. The same poll found that 50% of DP supporters opposed the alliance with the Communist Party, compared to 30% who favoured it.
By the 22nd, the Asahi Shimbun reported that Maehara had secured support from over 80 of 143 eligible Diet members, compared to under 30 for Edano. Edano attempted to counter this by appealing to local assembly and grassroots members, pledging to establish better communication: "We should start with this election by apologizing to local assembly members and supporters who expected much from the DP." Jiji Press reported on the 27th that 14 prefectural branches were supporting Maehara while ten were backing Edano, with 23 undecided.
Maehara won 502 of 834 points compared to Edano's 332, giving him a clear victory. He won 83 (62%) of the 134 votes cast by Diet members and 67% support from approved candidates. Eight members cast invalid votes, of which seven were blank and one was cast for Yosei Ide. Party insiders speculated that these members planned to leave the party after the election. He won 57% support from the grassroots membership and 55% of local assembly officials.
Among the party membership, Maehara won 37 prefectures to Edano's 10, performing best in his home region of Kansai, as well as Kyushu and Chà «bu. He also won Tà Âhoku, Chà «goku, and most of Kantà  and Shikoku. Edano's strongest prefectures were Hokkaido, Mie, and Okinawa. He also outpolled Maehara in his home prefecture of Saitama and in Tokyo.