Tokyo: Japan's new Environment Minister Shinjiro Koizumi, the son of charismatic former Japanese prime minister Junichiro Koizumi, is regularly rated by voters as the lawmaker they'd like most to see in the top job when Abe steps down.
Koizumi, 38, became the third-youngest lawmaker to join a post-World War Two Japanese cabinet when Abe announced a reshuffle on Wednesday.
Koizumi, popularly referred to as Shinjiro to distinguish him from his father, grabbed headlines last month with news he would marry soon and become a father.
He announced he would wed Christel Takigawa, 42, a French-Japanese television personality known as the face of Tokyo's successful bid for the 2020 Summer Olympics.
Koizumi was quoted in media as saying he was considering taking paternity leave after the child was born early next year, a controversial move in Japan where women are still often expected to take the lead in child-rearing.
He has spoken in favour of letting married couples use separate surnames, media reported, a practice banned for official documents under current law.
As environment minister, Koizumi could be in an awkward spot given Abe's commitment to nuclear power. The elder Koizumi, now retired from parliament, became a harsh critic of atomic energy after the 2011 Fukushima nuclear crisis.
The closest Koizumi had come to a cabinet post previously was his 2014 appointment as parliamentary vice minister for reconstruction of the tsunami-hit Tohoku region.
"Until now, Shinjiro has been mostly performance and it is not clear how much policy know-how he has," said University of Tokyo professor Yu Uchiyama. "Now that will become clear."
Koizumi has suggested in the past that taking a high-profile post too soon was risky, but some who know him said he might not want to wait too long before seeking the premiership.
"He's a young guy in a hurry," said one political source speaking on condition of anonymity.
Abe, who returned to power in December 2012 promising to reboot the economy and bolster defence, is on track to become Japan's longest-serving premier in November.
His tenure as Liberal Democratic Party leader, which ensures the premiership if the LDP stays in power, ends in September 2021. Party rules need to be changed if he wants another term.
Koizumi shares some of Abe’s conservative views — he has paid his respects at Tokyo’s controversial Yasukuni Shrine for war dead — but voted for a rival in a 2012 party leadership election. He has shaped his image as a reformer but taken care not to offend party elders.
Koizumi graduated from a private Japanese university in Japan and has a master’s degree from New York's Columbia University. In 2009 - the LDP was knocked out of power for three years - he won a lower house seat vacated by his father.