The mass shooting in Newtown, Conn., last December sparked a debate over gun laws. President Barack Obama called on Congress to act, and gun control advocates saw the moment as their best chance in years to take on the powerful fire arms lobby. But bipartisan legislation to expand background checks failed. Six months later, families of Newtown victims are back in Washington with hopes of re-starting the conversation. And they're not the only group fighting to keep momentum alive. New York City Mayor Michael Bloomberg is using his political leverage to target democrats opposed to gun control measures, a strategy some warn could backfire. Diane and her guests discuss efforts to reignite the gun control debate.