Yunus Qanuni is seen by many as President Hamid Karzai's main rival. A former education minister in Mr Karzai's interim administration, he is now the leader of his own party, 'The New Afghanistan'.
Mr Qanuni is an ethnic Tajik who won the backing of his old boss, former Afghan president Burhanuddin Rabani.
Mr Qanuni is a veteran of Afghan power struggles
Mr Qanuni is a former member of Shurai Nazar, a faction of Prof Rabani's Jamiat-e-Islami party led by commander Ahmad Shah Masood who was assassinated by suicide bombers on 9 September 2001.
He has also been supported by the former powerful Defence Minister, Mohammed Qasim Fahim.
Together with General Fahim and Foreign Minister Abdullah Abdullah, Mr Qanuni is the political and military heir of Ahmad Shah Masood.
Mr Qanuni was born in 1957 in the Panjshir Valley north of Kabul, but went to the capital to study.
He soon became involved in politics, opposing the rule of President Daoud, who had overthrown King Zahir Shah in 1973.
Fighting the Soviets
Following the Soviet invasion in 1979, he returned to the Panjshir Valley and joined up with Ahmad Masood's forces.
He is said to have travelled to Pakistan to buy arms and secure funds for Commander Masood, known as the "Lion of Panjshir".
In 1993, when the mujahideen took power in Kabul, he became joint defence minister in the government led by Mr Rabani.
The conflict between Afghan's warring factions was brought home to him when his car was blown up near Kabul in 1993, and he was seriously wounded.
Mr Qanuni impressed diplomats at the Bonn conference
After the fall of Kabul to the Taleban three years later, Mr Qanuni helped found the Supreme Council for the Defence of the Motherland, and later the United Islamic and National Front for the Salvation of Afghanistan.
Search for unity
He headed several Afghan delegations for talks with exiled leaders in Europe, including former king Zahir Shah, in an attempt to unite anti-Taleban factions.
Following Masood's assassination in September 2001, Mr Qanuni became the political head of the Northern Alliance's Shurai Nazar faction of Jamiat-e-Islami party.
He was named interior minister of the Northern Alliance when they re-entered Kabul on 13 November 2003 after the Taleban fled US-led forces, and headed their delegation to the Bonn talks.
At Bonn, diplomats were said to be impressed with his forceful speaking and negotiating skills.
But in a major setback to his political career, he resigned as interior minister during the emergency Loya Jirga, a move many believed he expected to win him support and an even higher position in the cabinet.
But Mr Karzai only offered him the ministry of education.
An upset Mr Qanuni threatened to resign but was persuaded to stay on by making him special presidential advisor on security issues.
In the 2004 presidential elections he ran against President Karzai by was defeated.
He then claimed to have turned down Mr Karzai's offer of joining his cabinet and vowed to form a strong opposition.
In the elections for speaker of the lower house of parliament, or Wolesi Jirga, he lost the support of one his main allies, Mohammad Mohaqiq.
Mr Mohaqiq - who was widely expected to be Mr Qanuni's main ally in strengthening the government opposition - joined the pro-Karzai hardliner Islamic leader Abdul Rab Rassoul Sayyaf.