What is the ruling on the prayer of the congregant if he learns that the Imam was not in a state of purity after the prayer has concluded?

Scholars have differed concerning one who prayed behind an Imam, then learned that his Imam was in a state of minor ritual impurity (hadath):

The Shafi'is and Hanbalis (and the view of a group of Companions and Tabi'in): His prayer is valid absolutely, based on the hadith: "They lead you in prayer; if they are correct, it is for you, and if they err, it is for you and against them." Abu Hanifa: The worshipper must repeat the prayer. The Malikis: The worshipper must repeat the prayer if the Imam intentionally led the prayer while aware of his state of ritual impurity; otherwise, not.

The most preponderant view is the first one.