Japan's ruling Liberal Democratic Party (LDP) officially launched its leadership election campaign on Monday amid a sharp decline in the number of eligible voting members. The contenders are Agriculture Minister Shinjiro Koizumi, former Economic Security Ministers Takayuki Kobayashi and Sanae Takaichi, Chief Cabinet Secretary Yoshimasa Hayashi, and former LDP Secretary-General Toshimitsu Motegi. All five also ran in last year's election, which saw a record nine candidates. The contest will focus on issues such as cooperation with opposition parties, economic measures to tackle rising prices, and rebuilding the party after successive election defeats and political funding scandals. The election, triggered by Prime Minister Shigeru Ishiba's announcement earlier this month that he will step down as the LDP head, will culminate in a vote on October 4. The winner is widely expected to be designated Japan's next prime minister by the Diet, given the LDP's status as the largest party -- despite the ruling bloc's recent failure to secure a parliamentary majority. A total of 590 ballots will be cast, split evenly between the 295 Diet member votes and another 295 ballots representing party member votes. Ballots from party members will be finalized the day before lawmakers vote on October 4, after which both sets will be counted together to decide the new party leader. Notably, significantly fewer members will be eligible to vote. According to data released Sunday by the LDP's election management committee, about 915,600 party members are eligible -- a drop of more than 140,000 from the previous leadership race. Party insiders attribute the decline to two factors: an overall decrease in LDP membership and a new rule requiring party members to have paid dues for at least two consecutive years to qualify. The shrinking membership base reflects broader challenges facing the LDP. Since the party was engulfed in a major "slush fund" scandal in late 2023, its ranks have thinned for two consecutive years. As of March this year, total party membership had already fallen below 1.03 million. SHOTLIST: FILE: Tokyo, Japan - Aug 14, 2024 1. Various of Liberal Democratic Party (LDP) headquarters; signs reading "Liberal Democratic Party" "Liberal Democratic Party headquarters"; security personnel; FILE: Lima, Peru - Nov 15, 2024 2. Then Japanese Prime Minister Shigeru Ishiba (L); FILE: Tokyo, Japan - April, 2024 3. Various of pedestrians, traffic; FILE: Tokyo, Japan - Date Unknown 4. Various of National Diet building, Japanese national flag; FILE: Tokyo, Japan - Date Unknown 5. Various of National Diet building; 6. Sign reading "The National Diet Main Gate"; FILE: Tokyo, Japan - April 29, 2024 7. Various of traffic; FILE: Tokyo, Japan - Date Unknown 8. Aerial shots of traffic, cityscape. [Restrictions: No access Chinese mainland]