Stephen Colbert is known for tearing apart politicians with an acerbic, unforgiving wit — a trademark that strikes fear in the heart of many a public official. “He’s clearly the most political late night host, and arguably the most partisan,” said Robert Lichter, director of the Center for Media and Public Affairs at George Mason University and the author of the forthcoming book “Politics Is a Joke: How TV Comedians Are Remaking Political Life.”