Japan's lower house has been dissolved for an expected snap October 22 election being called by Prime Minister Shinzo Abe as he seeks to confirm his mandate in the face a rising challenge from a popular new conservative party.
Abe, a conservative who returned to power in 2012, hopes a boost in his voter support in recent months will help his Liberal Democratic Party-led (LDP) coalition maintain a simple majority.
It currently holds a two-thirds majority.
A number of opposition MPs boycotted the session at which the lower house was dissolved on Thursday in protest at Abe calling the election and creating a potential political vacuum when tensions are high with North Korea.
"This will be a tough battle but it's all about how we will protect Japan, and the lives and peaceful existence of the Japanese people," Abe told MPs.
Popular Tokyo Governor Yuriko Koike's new Party of Hope, only formally launched on Wednesday, has upended the election outlook after she announced she would lead the group herself.
Koike, a former LDP MP and defence minister, said she would not stand for a seat herself but speculation she will persists.
A survey by the Mainichi newspaper showed 18 per cent of voters plan to vote for Koike's party compared with 29 per cent for Abe's ruling LDP.
Abe's personal ratings have risen to about 50 per cent from about 30 per cent in July, partly on the back of his leadership during the North Korea crisis.
The emergence of Koike's party, which she describes as pro-reform and conservative, has thrown the main opposition Democratic Party into turmoil.
The Democrats are struggling with defections and single-digit ratings and now appear in danger of being absorbed by the Party of Hope.
