There is something peculiar about truth... it is true no matter what. Truth from any source is still true.
In this, the election year, you will probably hear many attacks against the candidates character. Although these kind of things can help to establish patterns (like honesty, or overall laziness), they cannot however speak to the truth the candidates might be speaking.
For example, assuming base 10, 2 + 2 = 4 all the time. Not just some of the time; not most of the time, but all the time. If we speak to someone from my church and they say the answer is 4, this is correct the same way if we speak to someone from a mental asylum or a math genius and they say it is 4. Who the person is has no bearing on the truthfulness of the answer.
This can mean a lot to Christians. We need to evaluate things for the truth they correspond to. To attack some one's character instead of the merits of their argument is called the ad hominem attack.
Christians love to make ad hominem attacks because, I believe, it helps us to quickly resolve what we think about an issue. In this way we do not need to do the hard work of evaluating truth, instead we will measure character.
As Christ said he is the truth, we also should be striving to seek truth, and stand for truth. John 18:37 states Jesus came to "testify to the truth." This should be the goal of our lives. A Christian has no real room for the ad hominem.