Below merely summarizes my own thoughts on the church and political activism. I think Piper hits the nail right on the head regarding the power of the Church and its place in the political arena.
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"Don't press the organization of the Church or her pastors into political activism. Pray that the Church and her ministers would feed the flock with the Word of God centered on the gospel of Christ crucified and risen. Expect from your shepherds not that they would rally you behind political candidates or legislative initiatives, but that they would point you over and over and over to God and to His Word and to the Cross.Now, please try to understand this concluding point. When I warn you against politicizing me or politicizing the institution called Bethlehem [Church], or the Church in general, I do so not to diminish the Churches power but to increase it. The impact of the Church for the glory of Christ and for the good of the world does not increase when she shifts her focus from worship of God, winning of souls, and maturing and nurturing of faith, and raising up of a new generation. It doesn't! It feels in the moment like it does, "Hah, Look how many people showed up for the rally!" or, "Look at how many signatures they got in that church," or, "Look at how that committee is functioning..." it feels powerful! [But just] give it a generation, and little by little that vaunted power bleeds away the very nature of the Church and it's power.