Tobias Harris is a senior fellow at the Center for American Progress, an independent, nonpartisan policy institute. He is the author of "The Iconoclast: Shinzo Abe and the New Japan."

The race for the Liberal Democratic Party's leadership, which will be decided on Sept. 29, would appear to mark a generational shift for Japan's longtime ruling party.

Three of the four candidates -- Taro Kono, Sanae Takaichi and Seiko Noda -- would be the first prime minister born in 1960 or later. The fourth candidate, Fumio Kishida, would be only the second born after the LDP was established in 1955.

However, even as a new crop of leaders vies for the leadership, and with it Japan's premiership, the campaign has revealed that just over a year since Shinzo Abe's resignation, Japan's longest-serving prime minister continues to cast a long shadow.

It helps that Abe is a de facto leader of the LDP's largest faction, Hosoda, wielding tremendous influence over its decision-making even though he is no longer a formal member of the group. He is also the de facto leader of the LDP's right-wing, an influential minority within the party. Thanks in part to these roles, Abe has single-handedly boosted the leadership bid of Takaichi, a longtime ally.

With Abe's full-throated support, Takaichi has gone from a marginal candidate to a serious -- if still unlikely -- contender. Whether Abe can be called a kingmaker -- the party's divisions may make it difficult for anyone to assume such a role -- he is clearly determined to be a partisan combatant in the battle over his party's future.

But Abe's influence extends beyond his factional role. This year's leadership contest reveals the extent to which his premiership continues to shape and constrain the choices available to Japan's leaders.

With his legacy most obvious in macroeconomic policy, some candidates have been more explicit than others in acknowledging Abe's intellectual influence. Takaichi, for example, has referred to the three arrows of "Sanaenomics," but all four continue to operate in a policy environment of Abe's making.

The change in fiscal policy is especially striking. When he returned to the LDP's leadership in 2012, Abe inherited a party that had campaigned on fiscal consolidation and had maneuvered the Democratic Party of Japan into endorsing a consumption tax increase.

By the time Abe left office, his government's debt-financed measures to combat the Corona shock resulted in a record for Japanese government debt, which reached 1.2 quadrillion yen ($10.5 trillion) by the end of the 2020 financial year. Under Abe, the ruling party learned that Japan could in fact live with far more debt than textbooks suggested.

That Japan's government can do so is thanks in part to another Abe legacy, the Bank of Japan's use of what were once considered unconventional policy tools to become the dominant holder of the government's debts.

While not always popular, the BOJ's policies, centered on its yield-curve control program to target interest rates, are now a policy fixture. While the LDP's contenders fret about the bank's ability to achieve its inflation target and admit that monetary easing alone cannot create the sustainable growth that Japan needs, none has offered a credible program of his or her own.

Candidates for the presidential election of the LDP, left to right, Taro Kono, Fumio Kishida, Sanae Takaichi and Seiko Noda, pose with papers with their words on Sept. 18, 2021: none has offered a credible program of his or her own.   © Reuters

Meanwhile, although Kishida has declared that he would bring an end to "neoliberal" policy, the reality is that Abe already abandoned neoliberalism during his premiership.

The essence of the third arrow of Abenomics was that the government would use a variety of tools to channel economic activity to new sources of high value-added growth. While Yoshihide Suga embraced green growth as the focus for industrial policy, he did not break ranks with Abe's statist approach -- and there are few signs that Suga's successors will either.

Abe's influence over Japan's foreign policy choices may be no less total. Abe's strategic approach -- prioritizing ever-closer cooperation with Washington while building closer relationships with other Asian democracies such as the Quadrilateral Security Dialogue, or Quad, involving Japan, the U.S., India and Australia, and forging denser partnerships with the United Kingdom and European Union -- was followed closely by Suga.

Of the candidates vying to replace Abe, Kono and Kishida both served as foreign ministers in his cabinet, and will in all likelihood pursue a similar policy mix. The four candidates have also indicated their willingness to follow Abe's lead -- or even go further than Abe -- in boosting defense spending and acquiring new defense capabilities.

However, the most interesting aspect of the leadership race is what it reveals about the limits of Abe's influence. It is increasingly apparent that Abe left his successors a toolbox -- fiscal and monetary stimulus, state-led industrial policy, more activist foreign policy led by a strengthened prime minister's office -- but not a road map.

All the candidates will have to guide Japan through what they have warned is an increasingly dangerous world. It is unclear whether the potent tools Japan's next prime minister will inherit will be equal to its challenges, or whether new policy innovations will be necessary.

Just over a year after Abe left office, it is already clear that his successors will face a more anxious age than he did. But, for now, none of the candidates vying to lead Japan is prepared to part ways with his legacy.