Occasionally I host talk shows on a local Christian radio station, and whenever I do, without fail, someone will call into the program and complain about my "talking about politics when (I) should be talking about salvation." The compartmentalization of Christian faith from all other areas of "secular" life is nearly complete in the evangelical world.
Yesterday, a caller complained about my use of the terms "left" and "right," claiming that as Christians we ought not to get into these political differences, and that it was wrong to claim one side or the other for Christianity.
I certainly agree that we can't claim any particular political party for Christianity; there's no political party that is "God's party." But as far as "left" and "right" go, we can certainly claim one of them for Christianity. As I explained to the caller, here are the foundational, fundamental tenets of the two positions.
Left: Mankind is essentially good. Because of this basic goodness, man (and thus society) is ultimately perfectible under the right conditions.
Right: Mankind is essentially bad. Because of original sin, man is fallen. Without checks, he naturally tends towards the evil. He (and thus society) can never be perfected in this life, and thus we must take man's fallen nature into account in all governing endeavors.
Now, which view of mankind is laid out on every page of the Bible? If one claims that there is no Christian position on this, one is claiming that there's no biblical position on this. And if one is claiming that there's no biblical position on this, one has never even scanned the Bible.
It's almost superfluous to mention the fact that all of our empirical observations about man's nature also happen to support the view of the right. Those nations that have espoused the inherent goodness of man (which includes all Communist nations) have been responsible for more bloodshed in the last century alone than all other nations in world history combined.
There may be those on the left who believe in man's evil nature. And there may be those on the right who affirm the essential goodness of mankind. But if so, their political beliefs are not consistent with their foundational assumptions. If one believes that man is fallen and non-perfectable, something resembling conservatism must result--if he is at all consistent. And if one consistently believes that man is good and perfectible, something like liberalism must flow from it.
A Christian's foundational assumptions must be founded on biblical truth. Only one of these two positions is compatible with that.