In 2014, their rivalry resulted in a United States-brokered deal to share power, which was punctuated by five years of bickering.
And now Ghani and Abdullah are again disputing an election result.
Ghani is officially the winner – but only just, and that is rejected by Abdullah, who shares power with the president as a chief executive.
He is now threatening to form his own parallel government.
This political showdown could not come at a more critical time for Afghanistan.
The US and the Taliban appear close to an agreement that could lead to a planned reduction in violence, and if that posture is largely maintained it could be a pre-cursor to Afghan politicians sitting opposite the Taliban.
How can any of that happen, until we know: who runs Afghanistan?
Presenter: Peter Dobbie
Tamim Asey – Former deputy minister of defence and the executive chairman of The Institute of War and Peace Studies
Simbal Khan – Political and security analyst
Source: Al Jazeera News