Christ the King is a political as well as spiritual feast day
Pope Pius XI wrote encyclicals with some of the most interesting political ideas, in reaction to a time between the two World Wars in which political theory was debated strongly. He was the one who promulgated the feast of Christ the King, hoping that in doing so we could come to see that Christ is king of the world, king of our societies, king of our selves.
From Quas Primas, Encyclical letter proclaiming the Feast of Christ the King, by Pope Pius XI, promulgated on 11 December 1925:
To Our Venerable Brethren the Patriarchs, Primates, Archbishops, Bishops, and other Ordinaries in Peace and Communion with the Apostolic See.
1. In the first Encyclical Letter which We addressed at the beginning of Our Pontificate to the Bishops of the universal Church, We referred to the chief causes of the difficulties under which mankind was laboring. And We remember saying that these manifold evils in the world were due to the fact that the majority of men had thrust Jesus Christ and his holy law out of their lives; that these had no place either in private affairs or in politics: and we said further, that as long as individuals and states refused to submit to the rule of our Savior, there would be no really hopeful prospect of a lasting peace among nations. Men must look for the peace of Christ in the Kingdom of Christ; and that We promised to do as far as lay in Our power. In the Kingdom of Christ, that is, it seemed to Us that peace could not be more effectually restored nor fixed upon a firmer basis than through the restoration of the Empire of Our Lord. We were led in the meantime to indulge the hope of a brighter future at the sight of a more widespread and keener interest evinced in Christ and his Church, the one Source of Salvation, a sign that men who had formerly spurned the rule of our Redeemer and had exiled themselves from his kingdom were preparing, and even hastening, to return to the duty of obedience…[So] we deem it in keeping with our Apostolic office to accede to the desire of many of the Cardinals, Bishops, and faithful, made known to Us both individually and collectively, by closing this Holy Year with the insertion into the Sacred Liturgy of a special feast of the Kingship of Our Lord Jesus Christ…
7. It has long been a common custom to give to Christ the metaphorical title of "King," because of the high degree of perfection whereby he excels all creatures… But if we ponder this matter more deeply, we cannot but see that the title and the power of King belongs to Christ as man in the strict and proper sense too. For it is only as man that he may be said to have received from the Father "power and glory and a kingdom," since the Word of God, as con-substantial with the Father, has all things in common with him, and therefore has necessarily supreme and absolute dominion over all things created…
19. When once men recognize, both in private and in public life, that Christ is King, society will at last receive the great blessings of real liberty, well-ordered discipline, peace and harmony. Our Lord's regal office invests the human authority of princes and rulers with a religious significance; it ennobles the citizen's duty of obedience... If princes and magistrates duly elected are filled with the persuasion that they rule, not by their own right, but by the mandate and in the place of the Divine King, they will exercise their authority piously and wisely, and they will make laws and administer them, having in view the common good and also the human dignity of their subjects. The result will be a stable peace and tranquility, for there will be no longer any cause of discontent. Men will see in their king or in their rulers men like themselves, perhaps unworthy or open to criticism, but they will not on that account refuse obedience if they see reflected in them the authority of Christ God and Man. Peace and harmony, too, will result; for with the spread and the universal extent of the kingdom of Christ men will become more and more conscious of the link that binds them together, and thus many conflicts will be either prevented entirely or at least their bitterness will be diminished…
33. The faithful, moreover, by meditating upon these truths, will gain much strength and courage, enabling them to form their lives after the true Christian ideal. If to Christ our Lord is given all power in heaven and on earth; if all men, purchased by his precious blood, are by a new right subjected to his dominion; if this power embraces all men, it must be clear that not one of our faculties is exempt from his empire. He must reign in our minds, which should assent with perfect submission and firm belief to revealed truths and to the doctrines of Christ. He must reign in our wills, which should obey the laws and precepts of God. He must reign in our hearts, which should spurn natural desires and love God above all things, and cleave to him alone. He must reign in our bodies and in our members, which should serve as instruments for the interior sanctification of our souls, or to use the words of the Apostle Paul, as instruments of justice unto God [Rom. 6:13]. If all these truths are presented to the faithful for their consideration, they will prove a powerful incentive to perfection. It is Our fervent desire, Venerable Brethren, that those who are without the fold may seek after and accept the sweet yoke of Christ, and that we, who by the mercy of God are of the household of the faith, may bear that yoke, not as a burden but with joy, with love, with devotion; that having lived our lives in accordance with the laws of God's kingdom, we may receive full measure of good fruit, and counted by Christ good and faithful servants, we may be rendered partakers of eternal bliss and glory with him in his heavenly kingdom.
