Imam Ali (as) needed Shura To Become Calipah

To strengthen my opposition against the 12rs I've been reading an online book written by a shia scholar. The book is called The Role Of Aisha In The History by Allamah Sayyid Murtada Askari.

This book was always suggested by the shiachat member Aliyah. Of course back in the day,I didn't study Seerah to a high degree so, I was not ready for this book. However, under the company of scholars, I have the training needed to handle academic material.

Anyway the shia scholar quotes an incident which actually shows a flaw in the 12r shia sect's understanding of reality.

Ali and the issue of caliphate

Ali had no doubt that after the Prophet, the caliphate would belong to him and there would be no rival.(89) It was owing to this assurance that when his uncle al-’Abbas at the Prophet’s ablution ceremony said to him: “Give me your hand that I may swear allegiance to you so that the people would say that the uncle of the Prophet has sworn allegiance to his cousin. This would benefit you and no one would oppose you any longer,” he answered: “O uncle! Is there anyone beside me who covets the caliphate?”
He answered: “You will see soon enough.”

‘Ali said: “I have no wish to see the issue of my caliphate being settled behind closed shutters and I want all people to participate openly in it, and vote for me.” Then he remained silent.
http://www.scribd.com/doc/4558135/Allama-Sayyid-Murtaza-Askari-The-Role-of-Aisha-in-the-History-Volume-I

Now wait a minute. Wasn't Imam Ali (as) declared a Calipah in Ghadeer. According to the shias wasn't this an explicit statement ?

Looks like it making decision behind closed doors wasn't not accepted by Imam Ali (as) himself.