To begin, one must understand the meaning of "political allegory".
Allegory is a form of extended metaphor, in which objects, persons, and actions in a narrative, are equated with the meanings that lie outside the narrative itself. The underlying meaning has moral, social, religious, or political significance, and characters are often personifications of abstract ideas as charity, greed, or envy.
Thus an allegory is a story [any text so as to include poetry] with two meanings, a literal meaning and a symbolic meaning.
The word political simply means anything concerned with politics (activities associated with the governing of an area).
Therefore, a political allegory is a text whose meaning revolves around the governing of an area and contains an extended metaphor to describe the political attributes.
Keats' "Hyperion", given it speaks of a changing of power among the Roman gods, would make the poem one bearing a political nature. Unfortunately, it was not until Keats wrote "The Fall of Hyperion" that the poem became a political allegory.