Japan's ruling party votes on Wednesday for the country's next prime minister in an election that has turned into the most unpredictable race since Shinzo Abe made a surprise comeback almost a decade ago, defeating a popular rival in a runoff.

The winner of the Sept 29 contest to lead the conservative Liberal Democratic Party (LDP) is almost certain to succeed unpopular Yoshihide Suga as premier because the party has a majority in Parliament's powerful lower house.

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