Umar, the second caliph, was stabbed by a Persian slave in Medina in 644 and knew before he died that he would not recover. Unlike Abu Bakr, who had named him successor directly, Umar chose a different mechanism: rather than pick one man himself, he appointed six senior companions, Ali ibn Abi Talib, Uthman ibn Affan, Abd al-Rahman ibn Awf, Sa'd ibn Abi Waqqas, al-Zubayr ibn al-Awwam and Talha ibn Ubaydullah, and charged them with choosing the next caliph from among themselves within three days, under threat of execution if they failed to agree in time.
The six met in closed session, deliberately shielded from outside lobbying, though some reports describe pressure reaching them regardless. Talha arrived late, by most accounts after the substantive deliberation had already concluded, leaving the real choice to the other five. What made the process distinctive was its refusal to simply defer to seniority or acclamation: Umar had built in genuine deliberation, with a fixed deadline and a mechanism, Abd al-Rahman ibn Awf's deciding voice, for breaking a tie that everyone involved had agreed to in advance. It was, whatever its outcome, a real attempt at structured consultation rather than either inheritance or another improvised gathering like the one that had chosen Abu Bakr twelve years before.