It's not difficult to explain. In fact, it's intuitive. God's morality is an extension of His character. Since God is unchanging (e.g. immutability), and God and His morality are real: God's morality is normative (e.g. unchanging).
Jesus Christ's morality, as God, is God's normative morality. A godly normative morality is God's normative morality and when it is displayed by people, they are displaying God's normative morality.
Though no person is perfect you are incorrect to argue that it is impossible for a politician to display God's normative morality in their life because they have political affiliations. Some have and some do.
Note: The objectivity of truth that Christianity embraces is based on the premise that meaning is objective. This objectivity in meaning is rejected by much of contemporary linguistics; the prevailing conventionalist theory of meaning is a form of semantical relativism.
However, in addition to being an overreaction to platonic essentialism, conventionalism is self-defeating, for the very theory of conventionalism that "all meaning is relative" is itself a nonrelative statement. "All meaning is relative" is a meaningful statement intended to apply to all meaningful statements; it is a nonconventional statement claiming that all statements are conventional.
As such, it self-destructs, for in the very process of expressing itself it implies a theory of meaning that is contrary to the one it claims is true of all meaningful statements. The usages of symbols and words do change, but the meaning properly expressed by them does not.
Please explain, to me in the least, what 'a godly normative morality' means to you.
A good politician anywhere on earth:
has to belong to a certain group, side or camp.
has to follow a certain law that defines and organizes his group , side or camp.
has to fight, in a way or another, any enemies who may threaten the people he presents.
cannot love his enemies (Matthew 5:44) without risking being accused of treason.
I mean what you refer to as "a godly normative morality" is surely not the one revealed by Jesus Christ.
What do you think? Perhaps I missed things that you didn't.
Thank you.