The other question is whether a Christian should vote or serve on a jury.
Christ said that we are the salt of the world to preserve what is good, otherwise we should be cast on the dunghill. Matt 5:13
Christ said that we are the light of this dark world, and we must let our light shine before men for this reason:
Matthew 5:(16) Let your light so shine before men, that they may see your good works, and glorify your Father which is in heaven.
When we separate ourselves from this world to live in a separate kingdom, our lights are put under a bushel, and we do not glorify the Father.
The only way the early Christians could be martyred or persecuted for Christ was by being present in the world, and boldly standing for the cause of Christ. Is our separation from the world the reason there are no Christian martyrs today?
So is voting for a candidate, or casting your votes on a jury, are these activities not Christian?
The only example I know is that the apostles voted, or cast lots and prayed, to select Matthais as the 12th Apostle. (Acts 1:26).
When I imagine a world where Christians do not vote or sit on a jury, I see a world far worse than what we have today.
When I imagine a world where the non-Christians for some reason do not vote or sit on a jury, it would definitely be an improvement.
Just one Christian, sitting on a jury and saying "no", can stop a horrible misuse of justice.