TOKYO • He's young, good-looking and the media calls him "Japan's Macron", a reference to France's new president. So it is little surprise that lawmakers say Mr Shinjiro Koizumi may be offered a post when Prime Minister Shinzo Abe reshuffles his Cabinet next month in a bid to revive sagging public support.
Mr Abe wants to repair his popularity, battered by a scandal over suspected favouritism for a friend's business and by many voters' perception he takes them for granted after more than four years in office.
Mr Shinjiro Koizumi, the 36- year-old bachelor son of charismatic former premier Junichiro Koizumi, has been suggested as a future leader since being elected in a 2009 Lower House poll that temporarily ousted his Liberal Democratic Party (LDP).
But Shinjiro, as he is popularly known to distinguish him from his father, has acknowledged the risks of taking on a high-profile post too soon. "People often say, 'You're young, so you shouldn't fear failure,'" he told the Nikkei business daily in an interview in April. "But the ones who say that are waiting for you to fail. And if you fail, they will thoroughly beat you down."
Some in the ruling party warn that if Shinjiro accepts a key portfolio, it would have its downside, while perhaps not yielding Mr Abe a big boost in popularity.
"He's still young to be tasked with such heavy expectations," LDP lawmaker Hajime Funada told Reuters.
"It would be a difficult mission."
The closest Shinjiro has come to a Cabinet post was his 2014 appointment as parliamentary vice-minister for reconstruction of tsunami- hit north-eastern Japan.
Shinjiro shares some of Mr Abe's conservative views - he has paid his respects at Tokyo's controversial Yasukuni shrine for the war dead - but is hardly a protege of the premier, having voted for a rival in a 2012 party leadership election.
A fourth-generation lawmaker, Shinjiro has shaped an image as a reformer, while taking care not to offend LDP elders.
"Shinjiro has a passion and instinctive feel for politics," said a source, who declined to be identified for privacy reasons.
He has grabbed headlines for criticising the farm lobby that has backed the LDP but blocked efforts to reform the sector.
As head of a panel on redesigning social security to cope with Japan's ageing population, Shinjiro has suggested a "child insurance" scheme to fund free pre-school education with premiums, an idea more palatable to fiscal hawks worried about a huge public debt than the alternative of more government bonds.
He has been ambiguous on the politically touchy topic of nuclear power, however, seemingly caught between a government push to restart reactors and his father's campaign, following the 2011 Fukushima disaster, to abandon atomic power.
Shinjiro graduated from a private Japanese university and took a master's degree from Columbia University in New York. He then worked at a Washington-based think-tank before winning the Lower House seat left vacant by his father's retirement.