The contest to replace Yoshihide Suga as Japan’s prime minister kicks off on Friday with a four-way battle between a US-educated champion of deregulation, a sceptic of neoliberal policies and two outspoken female politicians seeking to become the first woman to take the top job.

With the Covid-19 crisis leaving the ruling Liberal Democratic party facing its biggest threat since it lost power to the opposition in 2009, the leadership race is the most unpredictable contest of the past 15 years. It will also be the first with two female runners in a country where less than 10 per cent of parliamentarians are women.

Some of the LDP’s largest factions — policy groups that have historically exerted influence in leadership contests — have failed to unify their members to back a single candidate.