Whilst democracy is considered by many to be the best available system of government it is nevertheless comprised of imperfect voters casting their votes for imperfect candidates who are fielded by imperfect parties.
A Christian who takes part in an election must decide with the help of prayer upon the best option available and if all options appear unacceptable then the only choice left is not to vote.
A Christian's loyalty must always and forever reside with the commandments of God and should any party be seen advocating the breaking of any of those commandments then they should not be supported.
For a follower of Christ there can be no such thing as a lesser of two evils. There is no halfway house that lies somewhere between righteousness and evil. There is no Heaven with even a little hell in it.
Perhaps this means that a Christian should never vote.
According to Romans 13:1-2 God himself institutes governments.
"1 Let every person be subject to the governing authorities. For there is no authority except from God, and those that exist have been instituted by God. 2 Therefore whoever resists the authorities resists what God has appointed, and those who resist will incur judgment."
Meaning that while God
may or may not agree with a particular government ideology like liberalism or conservativism, he does institute their existence.
It is my belief that Christians should always vote for the government God wants. While governments may have their hands in evil practices, they also do good things as well and are composed of imperfect people as you correctly stated.
Also, Christians should obey government regulations unless they require sinning by law. Peter, a disciple of the Lord, said in Acts 5:29 “We must obey God rather than men."
So in our effort to obey God rather than men, knowing that God institutes governments, should we make a prayerfully informed decision? Yes! I think so. Therefore, since people are imperfect no matter where we look to we should vote for the party who most closely aligns with the morality of God.
If we are looking for God-like perfection in a government then we will never find it on Earth unless God himself institutes it.