As part of the oath of office, members of the house and senate should swear to tell the truth, and nothing but the truth, whenever they speak on the floor of the house or senate or whenever they speak to their constituents,either directly or in the press.
Why is this important?
Members of the house and senate frequently lie, or make up 'facts" to promote a policy or law they are trying to pass for a special interest group of financial supporter, or to defeat a law they oppose for personal reasons.