CNN writes, (CNN) - The powerful National Rifle Association lobby should see Tuesday's outcome in a congressional election as a sign that their influence is declining, New York City Mayor Michael Bloomberg said, predicting future wins for pro-gun control candidates would require less than the $2 million he injected into this race. "I think it's a harbinger of what is going to happen here," Bloomberg said in an interview to air Wednesday on CNN's "The Situation Room."Follow @politicalticker Illinois state Rep. Robin Kelly defeated former U.S. Rep. Debbie Halvorson on Tuesday in a Democratic primary for the…