A leadership race is underway among Japan's opposition ranks. Two of the largest opposition parties are set to merge next week, when a lawmaker from one of the two groups is named its head.

Nearly 150 members of the Diet have registered to join the new political party, including more than 100 in the Lower House. This means it will have nearly as many Lower House seats as its precursor, the Democratic Party of Japan, just before the party took power 11 years ago.