times to there were stark differences on policy and approach, especially when it comes to fighting terrorist groups like isis. >> on our worse day, i think we have a lot more to offer the american people than the right wing extremists. >> reporter: hillary clinton and bernie standards face-to-face for the first time since a dispute over a breach of private voter files exploded in public. >> as soon as we learned that they looked at that information, we fired that person. >> does secretary clinton deserve an apology tonight? >> yes. i apologize. >> reporter: the debate comes as the focus of the 2016 race increasingly shifts towards national security and terrorism. >> we need to be united against the threats that we face. we need to have everybody in our country focused on watching what