Japan's ruling party will hold one of the most unpredictable leadership contests in decades on Friday, a race that could result in Japan's youngest or first female premier, or see a popular veteran succeed in his fifth and final leadership bid.
The scramble to replace current premier Fumio Kishida was sparked in August when he announced his intention to step down over a series of scandals that plunged the Liberal Democratic Party's (LDP) ratings to record lows.
Polls suggest three candidates have the edge in a record nine-strong field: ex-environment minister and heir to a political dynasty Shinjiro Koizumi, 43; economic security minister Sanae Takaichi, 63; and former defence minister Shigeru Ishiba, 67.
Whoever is chosen must quell anger at home over rising living costs and navigate a volatile security environment in East Asia fuelled by an increasingly assertive China and nuclear-armed North Korea.
The LDP, which has ruled Japan for almost all of the post-war era and has a majority in parliament, must hold a general election by October 2025. If Koizumi wins, he has pledged to hold a snap election that could come as early as next month.
"It's safe to assume that Ishiba, Takaichi, and Koizumi will do quite well, but I really cannot say who out of those three will win the race," said Yu Uchiyama, a professor of politics at Tokyo University.
"I don't think we'll know until the very last moment."
If no candidate secures a simple majority - which is anticipated due to the wide field - a run-off poll follows between the two candidates with the most votes.
In the run-off, 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. That result is due at 1530 JST (0630GMT).
Traditionally, powerful party factions have swung in cohort behind favoured candidates, making it easier to predict who might prevail.
While the influence of party elders will still play a role, most of these factions were recently disbanded following a scandal over unrecorded political donations, making this vote harder to predict, say analysts.
FRONTRUNNERS
Polls suggest Koizumi, the telegenic son of a former prime minister who governed between 2001-2006, has the most support among lawmakers. However some of his campaign pledges, such as reforming Japan's rigid labour rules, appear to have dented his grassroots following.
If he prevails, he would become Japan's youngest premier, surpassing the country's first ever prime minister Ito Hirobumi, who took office aged 44 in 1885, according to official records.
Ishiba, by contrast, has proved popular among the rank-and-file but has courted controversy with his peers for going against the grain and challenging previous leaders, and has failed in four previous leadership bids. He has said he will not run again.
Takaichi, a hardline nationalist and advocate of deceased former premier Shinzo Abe's "Abenomics" stimulus policies, could be the most consequential pick - not least because she would be the first female prime minister in a male-dominated society.
Her promise to reverse a trend of leaders avoiding the controversial Yasukuni war shrine if elected, could also sour relations with China, South Korea and others that view the site as a symbol of Japan's wartime aggression.
The last Japanese leader to visit the shrine, which commemorates war dead including those convicted by an Allied tribunal of war crimes after World War II, was Abe in 2013.
