After his wife, former congresswoman Gabby Giffords, was nearly assassinated two and a half years ago, former astronaut Mark Kelly became a gun-control activist who, with Giffords, founded a gun-safety organization called Americans for Responsible Gun Solutions. The couple is in Washington this week to lobby senators to support legislation to expand background checks for gun buyers. They have joined forces with another group activated by tragedy, the families of the Newtown victims, doubling down on the power of their collective experience in what history will record as the personalization of gun-control lobbying.