The ultimatum from the ruling ZANU-PF party on Sunday came after party officials dismissed Mugabe as their leader, further cornering the 93-year-old president in the wake of the army's takeover on Wednesday.
Political analyst Alex Magaisa said the military's surprise intervention, coupled with the ZANU-PF's moves against the man leading it for decades, "confirms that what Mugabe believed to be popular support was only a facade created by people in his party".
"Everybody else outside ZANU-PF was warning them that it was terrible to have a 94-year-old in 2018 as a candidate, but all these people were supporting him for their own interest," Magaisa, a lawyer and adviser to Morgan Tsvangirai, a former Zimbabwean prime minister, told Al Jazeera from Britain's capital, London.
Follow our live update here
Zimbabwe is expected to hold elections next year, but Magaisa raised questions whether that vote would be credible, even with Mugabe gone.
"It was always very doubtful whether there would be free and fair elections next year, given that the electoral landscape had not been changed significantly," he said.
"The removal of Mugabe would be an important part of changing that landscape, but we must understand that Mugabe was part of a system - that system hasn't changed," added Magaisa.
"The new actors who are coming in were part of the system that propped up Mugabe. The only question is, have they got the leadership to change the mindset, to change the way with which they approached elections and democracy? Are they born-again democrats or is it going to be the same?"
About Article Author