“Jesus is Lord” is the most widespread early Christian affirmation. It is central for Paul and for the rest of the New Testament. Like “Kingdom of God,” it has a political meaning as well as a religious meaning.
The key to seeing its political meaning is realizing that ‘lord’ was one of the titles of the Roman emperor: Caesar was called “lord.” To say “Jesus is Lord” is to say “Caesar is not lord.” To affirm the lordship of Christ is to deny the lordship of Caesar.
Indeed, several of the “titles” of Jesus in the New Testament were also titles of Caesar. ON coins and inscriptions, Caesar was referred to not only as “lord,” but also as “son of God,” “savior,” “king of kings,” and “lord of lords.” Caesar was also spoken of as the one who had brought peace on earth. Early Christian used all of this language to refer to Jesus. Even the Christmas tory, so politically domesticated in our observance, contains the challenge to Caesar. In Luke, the angel says to the shepherds, “To you is born this day…a Savior, who is the Christ, the Lord,” who will bring peace on earth. The titles of Caesar properly belong to Jesus.
Thus the familiar affirmation “Jesus is Lord”, now almost a Christian cliché, originally challenged the lordship of the empire. It still does. To use examples from more recent times, it is like Christians in Nazi Germany saying, “Jesus is mein Führer” – and thus Hitler is not. Or in the United States, it would mean saying, “Jesus is my commander in chief” – and thus the president is not. The lordship of Christ versus the lordship of empire is the same contrast, the same opposition, that we see in the Kingdom of God versus the kingdoms of this world.
Excerpted from The Heart of Christianity, Marcus Borg, p. 135-136