“Did the early medieval literature that you have read encourage Christians to exercise political leadership?”
Yes, certain pieces of literature did encourage Christians to be involved in political leadership. Justin the Mary Martyr and Polycarp, who was also a martyr, both encouraged Christians to stand up to bureaucrats who did not obey God.
Justin asked the bureaucrats to be pleasing to God. Polycarp did not obey the bureaucrats when they wanted him to deny God’s existence. Although from what I have read I believe these men did not directly tell Christians to exercise political leadership. These men were influencing Christians with their lives to rise up and stand by what they believed in. Justin and Polycarp are both very good examples to follow when it comes to how a Christian should react when being persecuted.
Christians need to stand up and defend their beliefs and their God given rights.