Japan’s incoming prime minister Shigeru Ishiba is poised to call a snap election for the end of the month, according to media reports, days after he promised to lift his party’s dwindling fortunes and “put a smile” back on the faces of the public. Ishiba, a moderate who saw off a rightwing challenge on Friday to become the new leader of the ruling Liberal Democratic party (LDP), will be approved as prime minister in parliament on Tuesday and appoint his cabinet later the same day. The 67-year-old former defence minister, who won the party leadership race at his fifth attempt, will try to seek an early public mandate on 27 October, the public broadcaster NHK and several newspapers said on Monday, more than a year before an election is due. Ishiba has said only that he would call a lower house election “as soon as possible”, but observers believe he wants to go to voters quickly, possibly to capitalise on his recent party victory and to give the main opposition Constitutional Democratic party as little time as possible to prepare under its new leader, Yoshihiko Noda. Ishiba could turn to one of his erstwhile leadership rivals in an attempt to revive the LDP’s fortunes after months of fallout from a fundraising scandal. Shinjiro Koizumi, who was knocked out of the contest after finishing third in the first round of voting, is expected to be made head of the party’s election committee, effectively making him the face of the campaign. Although the 43-year-old Koizumi, the son of the former prime minister Junichiro Koizumi, struggled to mount a credible challenge for the LDP presidency, he is popular among voters. Ishiba’s main rival for the LDP presidency, the ultra-conservative Sanae Takaichi, reportedly turned down the offer of a senior party post, the Kyodo news agency said, underlining the difficulties he faces in reuniting the party ahead of the rumoured general election. Takaichi, who lost to Ishiba in the second and final round of voting, was vying to become Japan’s first female prime minister. Reports suggest that the most senior posts in Ishiba’s cabinet will go to party heavyweights, including the former prime minister Yoshihide Suga, who is believed to have backed him in the leadership race. Ishiba is expected to unveil measures to help low-income households through the cost of living crisis and, on the foreign policy front, to pursue the creation of an “Asian Nato” to counter threats from China and North Korea.