Mayors Against Illegal Guns (MAIG), the pro-gun control group backed by New York City Mayor Michael Bloomberg, released an ad targeting Sen. Jeff Flake (R-Ariz.), one of the opponents of the Senate's high-profile background check amendment that failed last month.  The ad features Caren Teves, whose son, Alex, was killed protecting his fiancee in last summer's theater shooting in Aurora, Colo. ...