I don't believe that a sitting (standing?) Congress Critter can be charged with any crime for what they say on the floor of the Senate or House, nor do I think that they could be arrested for lying ever, unless it was an impeachable crime like lying under oath or obstruction of justice.
Slander, however, is probably doable if the CC in question spoke ill of a private citizen without cause or proof that what they were saying was true.
Congress Critters can and often do speak ill of each other or of groups that criticize them with relative impunity. They will often use harsh language when referring to public figures that have publicly disagreed with them and I have never heard of them being prosecuted for it. At worst they might, like Emanuele, have to apologize for a very poor choice of wording. Not to those they have insulted (Liberals), but to those who have worked for years to have a certain R word suppressed in favor of a more accurate term like Handicapped or Disabled.