I agree, but I have two quick thoughts:
1) If we, as evangelical, God-loving, God-fearing, America-loving Christians (sorry for the qualifications, but just saying evangelical or Christian really doesn't mean much anymore) only vote for the "perfect" candidate, we would never vote (and never could have voted - there has only been one perfect person to walk this earth, and He didn;t run for office). The result would be that our influence would be even more muted.
2) If we start listing the traits that a candidate MUST or must NOT have, we ignore the whole picture (i.e., good traits, the other candidate, etc.).
My approach is to trust God first and ask His direction. That way, my human biases and blind spots don't get in the way as much.
I believe that God instituted this great country, including our way of choosing leaders. In His omniscience, He knew there would be short-comings (humans are involved), but I believe it is the best form of government in which His people can be heard effectively. If we give up our right to vote, we ignore His hand in our formation.