I believe the Mahdi had already returned in the 1840's.
The Mahdi is Mohammed-Ali Hassan Al-Hilly, the interpreter of the Quran and the Bible.
He invited to the worship of God alone without associate, and had only few followers, although a large number of people admired his interpretation.
I tell you this story: I asked him about the Bahai, he said:
I went to one of their meeting halls in Mosul in Iraq, and I asked one of them: What's the proof of your claims?
The Bahai follower said: "Don't you read in the Quran 2: 2
So God says That book, and He did not say This book; therefore, "That book" indicates the Aqdas our book, because if it meant the Quran, then God would not say 'that', but would say 'this'!
Abu abd-Allah said: Do you know what is the meaning of the previous aya Alif, lam, miem?
The Bahai follower said: I don't know.
Abu abd-Allah said: It means:
Recite
To them, O
Mohammed.
So will Mohammed recite the Quran or recite your book the Aqdas?
At which the Bahai follower did not find any answer.
See the interpretation of these ayat here:
http://quran-ayat.com/pret/2.htm#a2_1
Mohammed-Ali Hassan Al-Hilly died in the year 1991 just after the invasion of Iraq by the First Zionist: Bush the father.
The second Zionist was Bush the son.