This is a loaded question, because politicians are notorious for saying one thing and doing another. Most have the uncanny ability never to tell the truth without ever lying, because they have a way with words. It is no wonder that they have such bad reputations. With that said, who can be trusted?
I would say there are a few important ways to determine this. First, we need to do fact checks. We need to examine what they say and see if they are telling the truth. Second, we need to look at their record and see if what they say has been backed up in the past. Third, we can also look at the opposite party and see what their opinions are of this particular politician. If there is even begrudging respect, this can say a lot. In the end, we need to do due diligence.