General Principles, Yes; Specific Policy, No
To further clarify my position, I want to draw a distinction between general principles and specific policy. I believe a local church has no business advocating specific policy, but it should state its support for general principles. For example, a local church should state the biblical principles regarding the sanctity of human life. I do not believe they should propose legislation regarding the outworking of that principle. This is simply a matter of integrity. While some members of a local church may have expertise in the area of establishing public policy, the church as a whole does not. That is not the church’s purpose, nor is it the church’s place.
Furthermore, a person’s stance on the best way for the government to protect the sanctity of human life is not a salvation issue. The church must always be a place where we allow for disagreement and discussion on a wide variety of things. As long as we all agree that Jesus is in charge, we need not all vote along the same lines.
The church should declare principles. The church should not design policy.
Having said that, each church should applaud and encourage those who feel called by God to give their lives to public service. There will be individual Christians and even Christian organizations who do have the level of expertise necessary to engage in debates over specific public policy. It may be that a large number of people within a local church feel similarly about a particular issue and band together, sharing knowledge and influence, to enact change at a legislative level.
This is very different from a local church being committed to one political platform.