Last Friday, Japanese Prime Minister Yoshihide Suga announced that he wouldn’t be contesting the ruling Liberal Democratic Party’s presidential election at the end of September. In doing so, he effectively signalled his intention to resign as Japan’s top leader after only a year in office.

The decision was unexpected, though not entirely surprising. A botched national response to the Covid-19 pandemic, and the almost routine scandals that seem to implicate the Japanese prime minister’s office, have resulted in increasingly poor polling for Suga’s government. Despite several bold and perhaps desperate moves to shore up his position in the LDP, Suga was eventually left with no option but to step aside.

With Shinzo Abe at the helm for most of the past decade, Australia could be forgiven for becoming accustomed to stability at the top of Japanese politics. But the departure of two prime ministers now in less than a year is worrying. A return to a pattern of frequent leadership turnover risks dulling Japan’s competitive edge in the Indo-Pacific. That effect could be magnified by persistent shortcomings in US regional strategy—gaps that Japan has filled for much of the recent past.

In fact, with the US largely absent from key regional forums in recent years, Japan under Abe came to be widely considered the de facto leader of the liberal order in the Indo-Pacific. Abe’s political longevity, adroit alliance management and strategic acumen ensured that the worst excesses of the US during Donald Trump’s administration didn’t critically undermine the regional order. Indeed, Tokyo was an indispensable partner for Canberra in getting the Comprehensive and Progressive Agreement for Trans-Pacific Partnership over the line, and Japan’s quiet but effective capacity-building, infrastructure and health initiatives have helped build stability in Southeast Asia.

Until the long-promised US rebalance to Asia truly materialises, if it ever does, the fact is Australia still needs a Japan capable of playing a major leadership role in the Indo-Pacific.

As my colleagues and I argue in our report Correcting the course, the approach taken by Joe Biden’s administration in the Indo-Pacific so far has lacked the sort of focus and urgency required to compete for regional influence. Questions loom over the administration’s capacity or willingness to develop a comprehensive regional trade strategy, for example. And repeat visits by cabinet officials to Singapore and Vietnam are no substitute for robust engagement with Southeast Asia more broadly.

These, unfortunately, are not new problems. And it’s therefore no coincidence that it is in these key areas that Japan’s regional activism has been of greatest value to Australia over the past decade—particularly since 2016. The risk now, however, is that persistent shortcomings in US Indo-Pacific strategy will compound with a sustained period of political bloodletting in Tokyo, with potential consequences for Japan’s regional strategy.

As Abe’s right-hand man, Suga was widely expected to ensure foreign policy continuity. And on that score at least, his tenure has been a success. Suga sustained Japan’s understated engagement in Southeast Asia and oversaw a notable hardening in Japan’s public posture on China’s coercive behaviour, particularly in the East China Sea and around Taiwan.

Importantly, Suga also doubled down on Australia–Japan ties. Ambassador Shingo Yamagami’s unprecedented public profile since his arrival in Canberra in January neatly demonstrates those efforts. It was no coincidence that Prime Minister Scott Morrison was the first foreign leader to visit Suga in Tokyo. And notwithstanding glacial progress on the reciprocal access agreement, new legal and operational accords have been struck to deepen engagement between the Australian and Japanese defence forces.

Even so, many predicted that Suga would serve only in an interim, ‘caretaker’ capacity, before making way for a more durable, empowered leader. But his departure nevertheless renews questions over whether the eight years of political stability at home and effective leadership abroad under Abe were an exception to the rule. There is no guarantee that Suga will not become the first in a new succession of ‘revolving door’ prime ministers.

A change of leader is unlikely to see Japan absent itself from the region in the same manner as America. Nor will it markedly change the overall trajectory of Japan’s regional strategy. But more frequent rotations of personnel through the Kantei and top foreign policy positions could, over time, dull Japan’s edge in regional competition with China and stall developments in key relationships, including that with Australia. It will not be a positive development if ministers who have paid particular attention to Australia, such as Defence Minister Kishi Nobuo, are replaced.

Suga’s successor will also assume power only months ahead of a general election. Experts have pointed out that although the government will almost certainly remain in power, a reduced LDP majority will make it harder to pursue ambitious defence and foreign policy goals, such as acquiring pre-emptive long-range strike capabilities. Tighter political margins may hamper the sorts of self-strengthening initiatives that enhance Japan’s strategic value to partners like Australia.

The challenges that awaited Suga as he entered office—a worsening public health crisis, perennial economic stagnation, acute demographic decline—will also confront his successor. Most of these issues are of greater public concern than Japan’s activities abroad.

Fortunately, there is a silver lining for Australia. Suga was generally regarded as more domestically oriented than his predecessor, but his replacement may be someone with greater experience and interest in foreign policy. And they may already be known to their Australian counterparts.

Two candidates stand out in this regard. The first, Administrative Reform Minister Taro Kono, is widely considered the frontrunner to succeed Suga. He served as defence and foreign minister in different Abe cabinets, and is a vocal advocate for intelligence-sharing between Japan and the Five Eyes nations, and of advancing defence cooperation with Australia. Kono was outspoken on the threats posed by China before the government’s change in tone and is known for straight talking on tricky issues in the US–Japan alliance. That quality would also be a valuable asset in navigating complex upgrades to the Australia–Japan relationship, such as those proposed by Ambassador Yamagami.

Fumio Kishida is also well known to Australia, having served as foreign minister between 2012 and 2017. Though considered less hawkish on China than his competitors for Japan’s top job, Kishida has nevertheless stressed the importance of maintaining the trajectory of Japan’s Indo-Pacific strategy (including its partnership with Australia) and of strengthening Japan’s defence capabilities to adapt to the deteriorating regional strategic environment.

It is in those interests that Japan’s regional partners will hope that whoever emerges as the next prime minister will occupy the Kantei for some time. But until that is assured, and until Washington gets its act together in the Indo-Pacific, Australia may yet face uncomfortable questions over the future of the leadership of the regional order.