1. God commands us to love our neighbors....it is difficult to say you love them if you don't stand up for righteous laws in civil government.
2. God commands us to love mercy, to do justly and to walk humbly with our God. You can't advocate or perform justice without getting involved in supporting just policies of civil government.
3. The great commission is for us to go into all of the world. The term ('world" actually means "order,") therefore what God is saying is that we should be affecting every arena of society throughout the world with the gospel
4. The gospel is the heart of the great commission, but one cannot know about forgiveness of sin until he understands what sin is. By standing against sin (e.g., corruption, abortion, obscenity, euthanasia, homosexual unions/marriage, etc...) in our civil government and culture, the church is actually helping to share part of the gospel.
5. Jesus commands us to be peacemakers, to stand up for and seek righteousness, to be “salt and light,” and to be "in the world" but not a part of it--these commands imply political participation at the very least.
6. Governments are a reflection of society. Many historians believe that the Protestant Reformation actually inspired the creation of democratic republics like the United States and most countries today. It is true that the early church was not involved in politics directly, but it is also true that they couldn't be involved since the civil government over them was not a democracy and was hostile to Christians.
7. An American Christian actually possesses two citizenships...one (and most importantly) heavenly citizenship, and two-US citizenship. Jesus told us to render unto Caesar (civil govt.) that which is Caesar's and unto God, that which is God's. Christians should at least vote and be active in encouraging righteous policies in government or else they are abdicating their responsibility as citizens and allowing the ungodly to control the nation.
8. Unless a Christian has become a monk, they reside and partake of the resources of the country and community in which they reside. If they can partake from the world, why can't they influence it for the kingdom of God? In other words, are we saying that it is OK for a Christian to partake of the world and the world's system, but it is not OK for them to change the world for the better—isn't the earth the Lord's?
9. There are no scriptures that prohibit God's people from being active in politics; in fact, we see Moses, Joseph, David, Solomon, Ezra, Daniel and Esther as integral parts of the government of their time! Paul appealed to Caesar for justice!
10. God's commands to promote and practice justice make it a necessity to be involved in the political process. It is my conviction that a Christian that does not vote (and vote for godly candidates and/or the candidate that stands for godly principles or at least more godly principles than their opponent) sins against God.
When the righteous rule the people rejoice, but when the wicked rule the people groan.