Harare - Zimbabwe's first lady said Thursday her 93-year-old husband should name a successor, wading into a subject that President Robert Mugabe has previously regarded as taboo.Grace Mugabe told members of the ruling ZANU-PF party women's league that naming a successor "will enable all members to rally behind one candidate," state broadcaster ZBC reported.Mugabe has repeatedly said he will not choose a successor. The world's oldest head of state has said he will contest next year's election. He has led the southern African nation since 1980.His wife has previously said her husband could rule even from the grave.This is the first time Grace Mugabe has publicly urged her husband to name a successor, although she did not say whether her statements were aimed at next year's election.Grace Mugabe, who heads the ZANU-PF women's league, has become increasingly powerful in politics in recent years. She said her husband's choice on a successor should be final.ZBC reported that she said naming a successor "has been the trend in other countries." She also used a biblical analogy of a son who organised a feast to crown himself because his father was sick.Some analysts have suggested that Robert Mugabe, who visibly struggles to walk these days, could call an early election.His party's secretary for administration, Ignatius Chombo, last month said Mugabe could call an election in February or March. He can only do that if Parliament chooses to dissolve itself. His party holds the majority in Parliament.The constitution stipulates the earliest date Mugabe can call an election is in July 2018.Fights to succeed Mugabe have intensified in recent months, with Cabinet ministers and military generals trading insults on mainstream and social media over the issue.