Former Japanese Defense Minister Shigeru Ishiba has given up on running in the ruling Liberal Democratic Party's upcoming leadership race and is leaning toward backing vaccination minister Taro Kono instead, people familiar with his decision said Tuesday.

Ishiba, the No. 2 pick to succeed outgoing Prime Minister Yoshihide Suga in opinion polls after Kono, had been considering putting his name forward for the Sept. 29 vote that will effectively determine the country's new leader, but some allies saw his chances of winning as slim and urged him to sit it out.

Former Japanese Defense Minister Shigeru Ishiba meets the press at the parliament building in Tokyo on Sept. 13, 2021, after meeting with vaccination minister Taro Kono ho declared candidacy in the ruling Liberal Democratic Party's leadership race on Sept. 29. (Pool photo)(Kyodo) ==Kyodo

The LDP presidential election now appears to be a three-way contest between Kono, former Foreign Minister Fumio Kishida and former communications minister Sanae Takaichi.

Earlier this month, Suga announced his intention to resign after just a year in office amid mounting criticism over his government's COVID-19 response.

The decision by Ishiba will likely help Kono, who was No. 1 in media polls including by Kyodo News, collect more votes as the LDP seeks to install a popular leader ahead of a general election this fall.

Having held a number of Cabinet and senior party posts including agriculture minister and LDP secretary general, and long considered a contender for prime minister, Ishiba, 64, made his fourth attempt at becoming LDP leader in September 2020 but came in last behind Suga and Kishida.

A divisive figure among LDP lawmakers, Ishiba's biggest source of power has been his popularity among the party's rank-and-file members, who will be voting in the LDP presidential election for the first time since 2018.

But Kono, 58, a fellow maverick within the conservative party known for his reform-minded views and social media savvy, is expected to sweep up many of those votes, leaving Ishiba with little chance of winning.

Even among the 17 lawmakers belonging to the LDP faction headed by Ishiba, some had argued he should seek to realize his policy goals by backing Kono.

Kono, who doubles as minister of administrative and regulatory reform, on Monday visited Ishiba's office to ask for his support should he choose to pass on the LDP presidential election.

Ishiba is set to announce his decision not to run at a press conference after meeting with his faction members on Wednesday.

Meanwhile, the faction led by former Chief Cabinet Secretary Hiroyuki Hosoda, the LDP's largest group with 96 lawmakers including former Prime Minister Shinzo Abe, agreed Tuesday to endorse both Kishida, 64, and Takaichi, 60, while leaving open the option for members to vote for Kono if they choose.

Environment Minister Shinjiro Koizumi, himself a popular choice for future prime minister, said he will back Kono, citing his experience in leading the vaccine rollout, focus on tackling climate change and willingness to change the status quo.

"With Japan and the world changing as it is amid the coronavirus pandemic, the LDP needs a new type of leader who is not held back by the old ways of doing things, the old ways of thinking," Koizumi said at a press conference.

Former communications minister Seiko Noda, who has expressed a desire to join the race, has yet to secure the 20 nominations from lawmakers necessary to throw her hat into the ring.

Suga, who has yet to publicly name his preferred candidate, behind the scenes has expressed full support for Kono, according to people close to the prime minister.

Campaigning for the LDP presidential election begins Friday, with LDP lawmakers of both houses of parliament and rank-and-file members each holding 383 votes for a total of 766.

The candidate who takes a majority of votes wins. If none is able to, the contest goes into a run-off vote between the top two competitors.

In the Kyodo News opinion poll, conducted in the two days following Suga's resignation announcement on Sept. 3, 31.9 percent of respondents said Kono was most fit to become prime minister, while 26.6 percent chose Ishiba and 18.8 percent selected Kishida.

Noda followed with 4.4 percent, while Takaichi trailed with 4.0 percent.

Related coverage:

Japan vaccine czar Taro Kono declares bid to succeed PM Suga

3-way LDP race likely as Kishida makes pledges, Takaichi declares bid

Taro Kono tops opinion poll as most fit to become Japan's next PM