There are narrations using the word WALI instead of caliph. It has same meanings.
Caliph of Prophet Mohammad is also WALI (master) of Muslim Ummah who is given right on believers more than themselves. We have discussed these things in our articles.
Our Sunni fellows always relate these caliphs with the Govt. which is not true. Please read our article Shia point of view about Caliphate – Imamate
Tafseer Ibn e Kathir mentioned narrations about Caliphate under the commentary of this verse (5:12) “Allah did aforetime take a covenant from the Children of Israel, and we appointed twelve captains among them.”
Ibn e Kathir also mentioned that Imam Mahdi is the one of those 12 caliphs. Ibn e Kathir tried his best to provide the list of those 12 Caliphs of Islam but he could not provide.
This is the big question for all Muslims to look for those 12 Caliphs, to figure out that caliphate which will not end until Imam Mahdi (as).
If our Muslim brothers can not find those 12 Caliphs after Prophet Mohammad (pbuh) then they need to acknowledge those Caliphs who are from the progeny Prophet Mohammad (pbuh) and they announced about themselves that they are the Caliphs of Prophet Mohammad. They are the WALI (master) of this Ummah.
We end this segment with the words of Imam Ali, the middle part of sermon 143 from Nahajul balagha.
” Where are those who falsely and unjustly claimed that they are deeply versed in knowledge, as against us, although Allah raised us in position and kept them down, bestowed upon us knowledge but deprived them, and entered us (in the fortress of knowledge) but kept them out. With us guidance is to be sought and blindness (of misguidance) is to be changed into brightness. Surely Imams (divine leaders) will be from the Quraysh. They have been planted in this line through Hashim. It would not suit others nor would others be suitable as heads of affairs.”
May Allah (swt) guide those who seek for truth and send blessings to holy prophet Mohammad and his Ahlalbait.