In some churches the congregation is homogeneous (everyone is pretty much the same race and political party), and in those churches it is easy to preach a message with political implications that resonates with the congregation.  However, the danger is the propensity to tell people what they want to hear, rather than what they need to hear.  In a diverse congregation it can be a challenge to walk the line between two (or more) perspectives, each with valid points, but neither wanting to hear anything that challenges their own views.  I find that expository preaching allows me to preach what the Word of God says, regardless of what anyone’s personal political point of view may be.  By preaching through books of the Bible in a systematic way, I cover the topics that the Holy Spirit moved the human author to pen.  I’ve learned to trust God to speak an on-time word even as I preach through a given book of the Bible.  It always seems to fit the occasion and speak life into our congregation, which is very diverse.