Abu Bakr radiyallahu ‘anhu was the right and most eligible caliph after the Messenger of Allah sallallahu alaihi wa alihi wa sallam. This is substantiated by a number of evidences, some of which are:
1. The consensus of all the companions to obey and submit to his orders and without any opposition. Had he been an oppressor who usurped the right of the caliphate they wouldn’t have left him without any revolt, nor would they have obeyed him, considering their steadfastness in religion and their fearlessness in taking action on anything in the name of Allah;
2. ‘Ali did not go against him nor did he fight him. And this stance from ‘Ali must be for one of three reasons: one, either for fear of the occurrence of any civil strife in the Ummah; two, due to his weakness and inability to fight; three: for his perfect knowledge of the fact that Abu Bakr was the right caliph and on the right track.
To say that he did not fight for fear of trouble and fitnah within the Ummah is, to say the least, vain talk, because he fought Mu’awiyah radiyallahu ‘anhu and a lot of people were killed in the battles that ensued between them, just like he fought Talha, Zubair and ‘A’isha radiyallahu ‘anhum at a time he was sure that the right of the caliphate was his, without fear of any strife.
It is also illogical to say that he did not fight due to weakness, because those who helped him in his battles against Mu’awiyah were believers on the day of Saqifah, as well as on the day ‘Umar was assigned by Abu Bakr to be his successor, and also on the day ‘Umar, on his death bed, ordered six people to deliberate on choosing one of them as the caliph after him. Had they known that the right to the throne was his they would have helped him against Abu Bakr because, had there been the purported nass(explicit order from the Prophet that ‘Ali should be the caliph immediately after him), Abu Bakr would have been more deserving to be fought than Mu’awiyah.
There is therefore no other reason behind ‘Ali’s stance but his knowledge of the fact that the right to the caliphate was Abu Bakr’s.
 Who fought for the blood of his kin ‘Uthman bin ‘Affan radiyallahu ‘anhu.