TOKYO — Shigeru Ishiba, a frank-speaking veteran politician and former defense minister, on Friday was elected leader of Japan’s ruling Liberal Democratic Party on his fifth try, besting eight other candidates and ensuring he will become the country’s next prime minister.

The 67-year-old succeeds Prime Minister Fumio Kishida, who last month decided against seeking a fresh three-year term as LDP president amid declining support for his cabinet resulting from a political funds scandal that has dogged the party all year. Ishiba is set to be elected prime minister on Tuesday in a vote in the Diet, a guaranteed outcome due to the LDP’s legislative majority.