According to the Qur'anic principle: "Their (i.e. Muslim's) affairs are based upon their mutual consultation", it was necessary that only that person be appointed their leader who enjoyed the support of the majority of the Muslims. It was precisely on this basis that the Prophet (pbuh) directed the Muslims to appoint their leaders from among the Qureish. The Prophet (pbuh) is reported to have said:

Your leaders will be from among the Qureish.

At another instance, the Prophet (pbuh) is reported to have explained the reason for this specification. The Prophet (pbuh) is reported to have said:

The people remain followers of the Qureish in this matter . Their Muslims remain followers of the Muslims of Qureish, while their infidels were the followers of the infidels of Qureish.

This narrative clearly indicates the fact that the Prophet's stated preference of the Qureish for the leadership of the Arabs, was due to the political support, which the Qureish enjoyed in the Arabian Peninsula. Thus, according the referred Qur'anic principle, under the prevalent political circumstance in the Arabian Peninsula, the Qureish were to be the - almost uncontested - ruling party. It was now the prerogative of the Qureish to elect the individual leader from among themselves. Had the circumstances remained under control, the various representatives of the sub-tribes of the Qureish would most probably have been consulted before the appointment of the leader. However, in view of the unusual circumstances, which developed at the Saqeefah Banu Saa`idah, the leader had to be urgently appointed, without the prior consultation of the representatives. However, subsequently all the representatives of the various tribes of Qureish, confirmed their approval of the decision that was taken at the Saqeefah, by pledging allegiance to Abu Bakr (ra).

Thus, the specification of the Prophet (pbuh) relating to the selection of the leaders from among the Qureish as well as the appointment of Abu Bakr (ra) as the leader of the Muslims, was, in fact, based on the referred democratic principle stipulated in the Qur'an.

It should, however, be kept in mind that under the prevalent technological structure, it was not possible to hold mass-level elections for the leader during those times. As a substitute to these elections, the representatives of various tribes would give the opinions on behalf of their tribes. Once it was determined as to which tribe would lead the collectivity, then it was the prerogative of the internal leadership of that tribe to select one person as the leader of the whole collectivity.

- Moiz Amjad, understanding-islam.com