Japan's next prime minister could be the youngest candidate in a crowded election for party leadership

Japan's ruling Liberal Democratic Party is set to elect a new leader in September and, by extension, the country's next prime minister.

With almost a dozen candidates set to enter the race, the field has been described by many analysts as competitive and unpredictable. The unusually wide and open contest is the result of attempts within the party to eliminate "factional politics," although faction-based ties still appear to remain strong. Factions are organized sub-groups within the LDP with their own leadership and policy goals.

One potential frontrunner is Shinjiro Koizumi, who is set to hold a press conference announcing his candidacy on Sept. 6.

The 43-year-old son of former premier Junichiro Koizumi is expected to be the youngest candidate in the contest. Along with 49-year-old Takayuki Kobayashi, who has already announced his candidacy, the two contenders are seen as the choices for generational change in the party election.

Koizumi, a former environment minister, is known for his advocacy of renewable energy. He has made headlines for surfing near Fukushima to help quell water safety concerns after the discharge of treated wastewater as well as being the first sitting cabinet minister to take paternity leave in Japan.

Rintaro Nishimura, a Japan-based analyst for The Asia Group said, while the public awaits formal announcements from would-be candidates, Koizumi is the closest to a frontrunner so far.

"His father's legacy, as a popular reformist populist LDP president/prime minister and the fact that he is seen, particularly in the current climate, as scandal-free and fresh-faced versus other candidates makes him an attractive candidate," he said.

Nishimura said Koizumi stands a good chance of gaining votes from both LDP Diet members as well as rank-and-file members across Japan.

The winner of the LDP election will need to secure a majority of the vote. If no candidate secures an outright majority, the top two vote-getters will go to a runoff.

"This time around as LDP Diet members look ahead to next year's general election, a lot of them are worried about their survival — whether they can hold onto their seat, especially younger Diet members who have held fewer terms in office," Nishimura said.

"I don't think the safe option is the option this time around, it is more about which candidate can win a general election, and in that case, someone who's popular, like Koizumi is naturally going to be one of the favorites."

Koizumi has also emerged as one of the most popular choices among the public. A poll conducted by local newspaper Asahi Shimbun found that Koizumi tied with Shigeru Ishiba in popularity nationwide with 21% each. Koizumi, however, saw the most support among LDP supporters polled with 28% compared with Ishiba's 23% share, according to the poll.

But there are questions around Koizumi's level of experience and policy outlook.

Tobias Harris, the founder of advisory firm, Japan Foresight, said in a recent online post, that while Koizumi has the "greatest potential to transform the race fundamentally," his resume is thin. He has not held a top party leadership position or a top cabinet posting.

"He is an effective campaigner and has worked on a range of issues, but his foreign policy experience is limited, which could be a particular weakness in an LDP leadership election that has already been affected by the U.S. presidential election and the prospect of a second Trump administration," Harris wrote.

There is also little known about his economic policies.

"Koizumi hasn't commented on BOJ policy normalization as far as I can tell" Harris told CNBC.

"We can make certain inferences — he's been concerned about fiscal policy and deficits, he has ties with [former defense chief] Shigeru Ishiba and others who were critical of Abenomics — but I don't think we know for sure. In general, the party is trending in favor of normalization, with the exception of the right wing."

Japan strategist Nicholas Smith from CLSA said it is too early for Koizumi to take the top job. 

"It's all about experience. He's been elected five times. That's the bottom end of what is acceptable," he said.

"On top of that, he's had one minor cabinet post in charge of nuclear power safety, but that is not a senior position. People will say, you can't be prime minister when you haven't done the other jobs."

The LDP election will be held on Sept. 27.