"It has been said that democracy is the worst form of government -- except for all those other forms that have been tried from time to time" (Winston Churchill).
There are three basic forms of government that can be considered. Each of them reveals something about our view of human nature. For example, if we are utterly pessimistic about human nature, we'll lean towards authoritarian governance, looking for ways to have the smart people impose their will on the rest of the world. Under an authoritarian regime, there are no checks and balances, no bill of rights, no free and fair elections. There is no trust. There is only suspicion of the consequences of human freedom and choice. There is no social discourse because the smart people do not believe they have anything to learn from the general population. An authoritarian government imposes its vision of society on people and coerces them into accepting that vision -- usually through violence and the denial of basic human rights.
If we are on the other end of the spectrum and are utterly optimistic about human nature, we may lean towards anarchy. The belief among some is that people are so good at heart that there is no need for laws. Just leave people alone, and they'll do the right thing. Structured government is seen as a hindrance to true personal freedom.
Personally, I cannot square either of these with what I know about human nature. Humans have immense dignity and are capable of great thought, sentiment and action. However, humans are also fallen and capable of tremendous acts of depravity. A Christian perspective of civil society must reckon with both of these facets of humanity. That is why Christians are so often associated with the spread of democracy.
There is a pretty broad spectrum of views within democracy -- from an emphasis on individual rights to an emphasis on communal good. At the heart of modern democracy, though, is the idea that we all listen to one another, using reason to persuade, discuss, critique and compromise.
The beauty of democracy (from a Christian perspective) is that it takes humans seriously -- refusing to govern people without their consent, giving them a share in the decision-making process. At the same time, because it understands the potential depravity of humans, it never concentrates power in one person or group. Reinhold Niebuhr said, "Man's capacity for justice makes democracy possible; but man's inclination to injustice makes democracy necessary."
Granted, democracy has often been hijacked and corrupted. But that only tends to happen when people refuse to be involved in the process. Democracy lends itself to conversation; it thrives on the involvement of everyone. Christians, therefore, help democracy flourish when they make a constructive contribution to the ongoing dialog in a pluralistic society, joining the conversations on war, divorce, abortion and education.
Christian involvement in democracy, thus, should not be seen as an attempt to gain power or control or to impose our vision of society on everyone else. This is part of being a good citizen and a good neighbor. This is part of what God calls us to do and be in this world. We are not merely concerned with getting as many people on the life boats as possible, preparing them for the life to come. We are also concerned with life in the here and now, making life on this earth reflect God's original intent.