How did Uthman assume the Caliphate?

After the assassination of Umar ibn al-Khattab, may Allah be pleased with him, he made the caliphate a matter of consultation (shura) among six of the Companions. Some of them entrusted the matter to others, and then Abd al-Rahman ibn Awf withdrew his right and consulted the people for three days and nights. He did not find two people disagreeing on presenting Uthman ibn Affan, except for what was narrated from Ammar and Miqdad that they suggested Ali ibn Abi Talib. On the fourth day, Abd al-Rahman ibn Awf gathered Ali and Uthman in the mosque and offered them the allegiance based on the Book of Allah, the Sunnah of His Prophet, peace and blessings be upon him, and the actions of Abu Bakr and Umar. Uthman agreed, while Ali refused to answer except to the extent of his effort and capacity. So Abd al-Rahman ibn Awf pledged allegiance to Uthman, and the people followed suit with their allegiance. Thus, Uthman's caliphate was completed with their consent and choice.