Is the expected al-Mahdi an imam and a caliph?

The questioner : As for al-Mahdi, you said that he is a scholar and a reformer, but you did not use the word "imam" or "caliph" for him. Does this mean that al-Mahdi is not a caliph?

The Shaykh : It is obligatory, it is obligatory that he be a caliph.

The questioner: Yes.

The Shaykh : Yes, exactly.

The questioner : ... A small question.

The Shaykh: Yes.

The questioner : Regarding giving us a brief overview of

The Shaykh : Come on, Abu Mahmud, you will keep us up all night with this, ha ha ha.