The author of Al-Manar says: "I am certain that if the issue of imamate was among the issues openly asserted in the Holy Qur'an, there would have been no discord among Muslims after the demise of the Prophet. But, as we see, there is a discord, and Imam Ali did not refer to this verse to prove his legitimate right for leadership of the Muslims. Also none of the Infallible members of the Household of the Prophet and his companions who preferred Imam Ali over others referred to this verse."[1]
Response:
This approach to interpretation lacks the most basic principles and preliminary requirements of interpretation. History, cause of revelation of a verse... are among the basic sciences of Qur'anic interpretation. It is necessary for a commentator to know these sciences for interpretation of any verse of the Holy Qur'an. Of course, we all know that loving something more than enough will cause him to close his eyes to realities so that he sees everything supporting it as extremely good and anything opposing as something very bad.
After 25 years of staying aloof from power, Imam Ali (A.S) was invited by the people to take care of their affairs. He addressed a sermon in 35th Hegira in Kufa, in the presence of 24 renowned companions of the Prophet (PBUH). In that sermon, Imam Ali (A.S) referred to the rightfulness of imamate and to prove it, he referred to the Verse of Proclamation and traditions on Ghadir Khumm. The companions approved him all in that gathering. This is, of course, apart from his reasoning to the Verse of Proclamation in Saqifah Bani Saedeh and many other times, when he used Qur'anic verses and traditions to prove his legitimate right for leadership of Islamic Ummah.[2] All these indicate that unbiased interpretation of the Qur'an would support Imam Ali's succession to the holy Prophet (PBUH).
source : www.tebyan.net