The onus is upon whoever says: "Abu Bakr, then 'Umar, then 'Uthman, then 'Ali" regarding superiority. The evidence for that is that 'Ali is the most superior of those who remained after 'Uthman, by the consensus of the Companions of Muhammad, may Allah bless him and grant him peace.
التَّبِعَةُ عَلَى مَنْ قَالَ: أَبُو بَكْرٍ وَعُمَرُ وَعُثْمَانُ وَعَلِيٌّ فِي التَّفْضِيلِ وَالْحُجَّةُ فِيهِ أَنَّ عَلِيًّا أَفْضَلُ مَنْ بَقِيَ بَعْدَ عُثْمَانَ بِإِجْمَاعِ أَصْحَابِ مُحَمَّدٍ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ
