Why did Japanese Prime Minister Shigeru Ishiba resign? And who might replace him?

Japanese Prime Minister Shigeru Ishiba has bowed to weeks of pressure from within his party and announced his resignation, less than a year after taking office.

His departure plunges Japan back into political uncertainty, reviving fears of a return to the revolving-door prime ministers who dominated the 1990s and late 2000s, before Shinzo Abe restored stability in 2012.

Whoever succeeds him must not only steady the Liberal Democratic Party (LDP), but also restore public trust in a political system battered by scandals, factional infighting and rising voter scepticism about one-party dominance.

Why is Ishiba leaving?

Ishiba took office only last September, after Fumio Kishida stepped down amid a string of scandals.

He inherited a deeply troubled party. Kishida was forced out in 2024 after revelations of extensive ties between the LDP and the Unification Church. The church had long been controversial in Japan, but became even more so after Abe’s assassination in 2022 by a man who held a grudge against it. The church’s ties to the LDP were revealed shortly thereafter.

A slush-fund scandal further eroded public trust in the party. Ishiba promised reform and stricter accountability — but that stance angered many senior figures, especially those implicated in the scandals he sought to confront.

The LDP lost its lower-house majority soon after his election, followed by further setbacks, including a defeat in the July upper-house poll. Calls for Ishiba to quit grew louder, with party heavyweights warning of a split in the conservative base if he clung to power. Over the weekend, he finally surrendered.

Ishiba justified the timing by pointing to the risk of a political vacuum during ongoing trade talks with the United States. With an agreement on tariff reductions concluded last week, he yielded to critics without resorting to the traditional prime ministerial weapon of dissolving parliament to silence his rivals.

The decision may appear puzzling. Recent polls showed Ishiba’s popularity edging upward, suggesting ordinary voters were warming to him.

But his downfall underlines how much sway the LDP’s old guard still holds behind the scenes, prioritising internal discipline over electoral momentum.

Koizumi vs Takaichi

The leadership race is already underway, with a vote expected in early October. Two names stand out.

On one side is Shinjiro Koizumi, 44, son of former prime minister Junichiro Koizumi. Representing the party’s more liberal wing, he has previously expressed support for same-sex marriage and allowing married couples to use separate surnames – positions that set him apart in the LDP.

As agriculture minister in Ishiba’s government, he won recognition for tackling rising rice prices and pushing reform in a sector long tied to LDP patronage politics.

Charismatic and popular with voters, Koizumi has cultivated ties with the opposition Japan Restoration Party. This support could prove crucial in the LDP forging a new coalition or shoring up its minority government with its coalition partner, Komeito, which would still need opposition backing to pass legislation.

If chosen, he would become Japan’s youngest-ever prime minister.

On the other side stands Sanae Takaichi, a staunch conservative who finished runner-up in last year’s leadership race.

A self-styled heir to Abe’s legacy, she opposes same-sex marriage and dual surnames, favours constitutional revision to clarify to the role of the country’s Self-Defense Forces, and regularly stresses the need to strengthen Japan’s military posture.

She has likened herself to former UK prime minister Margaret Thatcher, calling for bold fiscal spending and monetary easing to drive growth.

If elected, she would become Japan’s first female prime minister, though her hardline positions could strain ties with coalition partner Komeito.

A TBS poll this week puts Koizumi and Takaichi neck-and-neck, each at 19.3%, while a Nikkei survey from August 31 gives Takaichi a slim lead at 23%, just one point ahead of Koizumi.

Other contenders may emerge, including Chief Cabinet Secretary Yoshimasa Hayashi. Much will depend on the LDP’s choice of election format: whether rank-and-file members get a say, or only lawmakers in parliament.

Either way, candidates need the support of 20 members of the Diet (Japan’s parliament) to enter the race.

High stakes for Japan’s ruling party

The stakes could not be higher. With Ishiba’s departure, hopes of reforming the LDP have faded.

If the new leader fails to regain public confidence, the party risks falling victim to its own long dominance. To maintain power, it has been locked into defending the status quo, while new right-wing populist challengers, such as Sanseito, gain ground with anti-foreigner rhetoric.

With the next elections not due until 2028, Japan is entering another uncertain political chapter. Whether the LDP emerges strengthened or weakened will depend not just on who replaces Ishiba, but on whether the party can convince a sceptical public it is still capable of renewal.