How was Uthman ibn Affan chosen as a caliph?

Uthman ibn Affan (ra), the third caliph, was chosen by a council meeting in Medina, in northwestern Arabia, in AH 23 (643/644). The second caliph, Umar ibn al-Khattab (ra), was stabbed by a  Persian slave. Mindful of the tumults that had occurred after the death of the Prophet (saw), on his deathbed Umar (ra) appointed a committee of six men, to choose a new leader. At his death bed, Umar ibn al-Khattab (d. 644) nominated a board of six members who were required to elect one of themselves as the next caliph. The group consisted of Sa`d ibn Abi Waqqas, Abdur Rahman bin Awf, Zubayr ibn al-Awwam, Talha ibn Ubayd Allah, Ali ibn Abi Talib and Uthman ibn Affan. To regulate the group and ensure no single person would stop the process, Umar said they should all agree unanimously on the next caliph or if they disputed beyond 3 days and 2 nights, those disputing would be killed. Out of the six members, Zubair withdrew his candidature in favor of Ali. Sa'd ibn Abi Waqas withdrew in favor of Uthman. Out of the three remaining candidates Abdur Rahman decided to withdraw, leaving Uthman and Ali. Abdur Rahman was appointed as the arbitrator to choose between the remaining two candidates. Contacting the two candidates separately, he put to them the question whether they would follow in the footsteps of the previous caliphs. Ali said that he would follow the Qur'an and the Sunnah of the Prophet (saw). Uthman replied to the question in the affirmative without any reservation. Thereupon, Abdur Rahman gave his verdict in favour of Uthman. An accepted Sunni version of this account shows a tie in votes between all three Uthman, Abdur Rahman and Ali where Uthman and Ali voted in favour of their respective partner in the elections. Then Abdur Rahman suggested to allow him to withdraw his candidature at the cost of the choice for leadership between the two remaining candidates. He was allowed to do so and he chose Uthman as the new caliph. Source: Wikipedia