A member of the ruling Liberal Democratic Party (LDP) who does not belong to any faction, Mr Suga has been approached by leaders of other party wings as someone who can ensure the continuation of Mr Abe’s policies, including Japan’s security alliance with the US, the coronavirus pandemic and measures to shore up the economy.
Mr Suga, 71, is a familiar public figure thanks to his televised matter-of-fact daily media briefings.
He is set to announce his candidacy and key policies later on Wednesday, a day after former foreign minister Fumio Kishida and ex-defence minister Shigeru Ishiba expressed their intention to run for the post.
Ruling party executives have decided that the September 14 vote for the party leader – and consequently the prime minister – will be limited to MPs and selected prefectural representatives.
Mr Ishiba is not seen as popular among LDP parliamentarians due to his anti-Abe stance, but he is a favourite in public opinion polls.
The son of a strawberry grower in the northern prefecture of Akita, Mr Suga is a self-made politician, a rarity in Japan’s largely hereditary business of politics.
He earned his own tuition while working several part-time jobs to graduate from a university in Tokyo, entering politics as secretary to an MP for 11 years and serving as a city assemblyman for nearly nine years before he was elected to parliament in 1994.
As Japan’s longest-serving chief cabinet secretary, Mr Suga is a policy coordinator and adviser to Mr Abe – the point man behind the centralised power of the prime minister’s office that influences bureaucrats to implement policies.
Mr Suga is also known to have helped smooth out differences by keeping close ties with both LDP heavyweight Toshihiro Nikai and a centrist coalition partner, Komeito.
He has earned a reputation for his matter-of-fact twice-daily televised media briefings.
The cabinet secretary has become known as “Uncle Reiwa” after he was tasked with unveiling the new imperial era name for Emperor Naruhito last year.
Despite his soft-spoken and low-key image, Mr Suga, who is also in charge of Okinawa, has offended local leaders with his heavy-handed approach to push the central government’s policy in a dispute over the relocation of a US marine air station to another spot on the southern island.
Mr Suga also invited protests last year over his hostile responses to a newspaper reporter asking tough questions criticising Mr Abe’s policies.
However, Mr Suga has been a loyal supporter of Mr Abe since his first stint as prime minister from 2006-2007, which abruptly ended because of Mr Abe’s chronic illness, and helped him return to power in 2012.
Mr Abe, who has had ulcerative colitis since he was a teenager, last week announced he would resign.
Asked about key policies that a post-Abe government should tackle, Suga noted coronavirus measures as the biggest challenge.
The Japan-US security alliance, developed through the friendship between Mr Abe and US president Donald Trump, “needs to be further deepened” within the limitations of Japan’s pacifist constitution, he said.
The two other contenders, Mr Kishida and Mr Ishiba, said that Mr Abe’s policies tended to ignore the voices of ordinary people and that they intent to address the economic and social divisions that had widened under him.
Neither man has proposed any major changes in Japan’s security and diplomatic policies.
The next prime minister will finish the rest of Mr Abe’s term, until September 2021. There are no women contenders.
