How will Japan pick its next leader?

The process to pick Japan's next leader is more complicated than before as Ishiba's Liberal Democratic Party (LDP), which has ruled Japan for most of the post-war period, and its junior coalition partner lost their majorities in both houses of parliament during his tenure.

PARTY LEADERSHIP RACE

First, the LDP must pick a new president to replace Ishiba. The date has not been set yet.

In the last party leadership race in September 2024, candidates needed to secure 20 nominations from the party's lawmakers to be eligible to run.

The party plans to hold the vote on October 4, broadcaster TBS reported, citing an unnamed senior party official.

Candidates will embark on a period of debates and campaigns across Japan, culminating in a vote by lawmakers and rank-and-file party members. In the last race, there were nine contenders, and Ishiba won in a run-off.

LDP VOTE

The party can choose its next leader through two formats: a "full-spec" election or a quicker, simplified vote.

In a full-scale contest, used during the last leadership race, each lawmaker casts a vote, with rank-and-file members also receiving an equal number of votes in the first round.

A candidate securing a simple majority in that poll becomes party leader. If no one secures a majority, a run-off follows between the two candidates with the most votes.

In that second round, each lawmaker again gets one vote, but the share of the rank-and-file drops to 47 votes, one for each of Japan's prefectures.

A simplified election is a smaller contest typically employed after a sudden resignation. It limits voting to LDP legislators and three representatives from the party's prefectural chapters, bypassing a vote by the broader membership.

The party last used this 'simplified' method in 2020 to select Yoshihide Suga as its new leader following the resignation of Prime Minister Shinzo Abe.

In the unlikely event of a tie, the winner will be decided by lot. That has never happened in a leadership contest, but was used in 2010 to decide who would chair the LDP's upper house caucus.

PARLIAMENT VOTES

Since the ruling coalition has lost its parliamentary majority, the next LDP president is not guaranteed to become prime minister, although that is likely as the party remains by far the largest in the lower house.

In 1994, the LDP formed a three-way alliance with its arch-rival, the Japan Socialist Party and a smaller startup party to regain power, having socialist leader Tomiichi Murayama elected as prime minister.

Based on precedent, the more-powerful lower house will first vote on its choice for prime minister. Lawmakers can nominate any candidates from the chamber, and historically the leaders of opposition parties have been put forward for the vote.

Any candidate who secures a simple majority in the first round wins approval. If no one secures a majority, a run-off poll follows, between the two candidates with the most votes.

Voting then passes to the upper house, where a similar process begins, although only members of the lower house are eligible to be prime minister.

If there is a disagreement between the houses, the choice of the lower house prevails. This happened in 2008 when the lower house chose the LDP candidate and the upper house picked an opposition candidate.

The new prime minister may also call a snap general election to seek a national mandate.