Since I’m not Reformed, I have no impediment to criticizing Dr. Horton’s 2 kingdom’s view.
First, it’s utterly unsupported by the actual stories of the bible. Whether Joseph and Pharaoh, David and Samuel, Hezekiah and Isaiah, Daniel and Babylonian Emperors, Esther and the King, Jesus and Pilate, James and Herod, Paul and Felix, and maybe even John and the Emperor, there is no shortage of God-believers involving themselves in affairs of state.
Jesus’ words to “render to Caesar what is Caesar’s” does not say to be uninvolved as citizens. There is no doubt, of course, that Christianity is not about taking over kingdoms and forcibly subjecting them to our beliefs. (We’ll leave that to Islam.) Christ’s intent was that believers actually believe, not that they be forced to say they are believers.
To say we are to withdraw from the reality of the political responsibilities that are upon us is no different than saying we should withdraw from the responsibility to help fight a fire at our neighbor’s house.
Truly, Christians must be involved in the political process.
Just one clarification — being Reformed definitely does not require one to believe “Two Kingdoms” theology. Many conservative Calvinists believe that Dr. Horton and the Westminster-West people have imported a Lutheran view of the state. I do not understand Lutheran doctrine well enough to make that claim and I don't want to bear false witness against Lutheran brothers. I'm “pinging” a Freeper who is a Missouri Synod Lutheran, Rev. Charles Henrickson, to see if he wants to comment.
I do know Reformed doctrine well enough to believe that “Two Kingdoms” theology, especially in its more radical forms, cannot possibly be reconciled with what Ulrich Zwingli did in Zurich, what John Calvin did in Geneva, what John Knox did in Scotland, what the Dutch burghers did in the Netherlands, and what the Puritans did in England and New England. I cannot imagine how anyone can say with a straight face that Calvinists historically did not believe their faith had direct political implications.
Some of the “Two Kingdoms” people admit that the “Old Calvinists” were, in their words, “theocratic” but say the American revisions of the Westminster Confession make that unnecessary to believe anymore. Others, including a Ph.D student in my own theological circles, are making serious efforts to prove that John Calvin himself advocated “Two Kingdoms” theology. I plan to read his doctoral dissertation or subsequent books, but I just don't see it.