Secret Service director Mark Sullivan appeared before Congress yesterday for the first time since his agency's Colombian prostitution scandal came to light.  Sullivan was testifying before the Senate Homeland Security Committee and  insisted time and time again that the incident was an isolated event and that it was not indicative of larger problems within the Secret Service. Sullivan… who was testifying before the Senate Homeland Security Committee… insisted time and time again that the incident was an isolated event and that it was not indicative of larger problems within the Secret Service    Takeaway Washington Correspondent Todd Zwillich sat in on the hearing and joins to discuss.