The odds are high that Prime Minister Shinzo Abe will be put on the defensive heading into the ordinary Diet session, as opposition party lawmakers appear to have plenty of ammunition to use against him.

Despite his increased calls for Diet debate on his long-held goal of constitutional reform, Abe will have to spend some time trying to stem a further fall in his support ratings resulting from a spate of simmering scandals.

The key question is when Abe might shift from a defensive posture and call an election.