The nature of the tragic hero is that he is a person greater than average in terms of power, intellect, and strength, who ends up enduring suffering, partially due to fate and partially due to the nature of his own character. Thus the play begins presenting Oedipus at the height of his power, as the man who saved Thebes by answering the riddle of the Sphinx.
The priest wants Oedipus' help in defeating the plague.To obtain it, he uses flattery in three ways. First, his emphasis on how Thebans look up to and depend upon Oedipus flatters his ego. Next, in praising Oedipus, the priest holds up a mirror to how Oedipus should behave in this crisis. Finally, he appeals to Oedipus by suggesting that he will become an ideal to posterity as well as to the present if he saves Thebes from the plague, and thus portrays the present ideal as something that could be tarnished if Oedipus does not continue to benefit Thebes, saying
Don’t let our memory of your ruling here
declare that we were first set right again
and later fell.