Sen. Susan Collins, R-Maine, right, introduces Sen. Bill Nelson, D-Fla., during a news conference on Capitol Hill in Washington, Tuesday, June 21, 2016, to unveil a new gun legislation proposal. From left are Nelson, Sen. Tim Kaine, D-Va., Sen. Martin Heinrich, D-N.M., Sen. Jeff Flake, R-Ariz., and Collins.
Sen. Susan Collins, R-Maine, right, introduces Sen. Bill Nelson, D-Fla., during a news conference on Capitol Hill in Washington, Tuesday, June 21, 2016, to unveil a new gun legislation proposal. From left are Nelson, Sen. Tim Kaine, D-Va., Sen. Martin Heinrich, D-N.M., Sen. Jeff Flake, R-Ariz., and Collins. Evan Vucci AP
Sen. Susan Collins, R-Maine, right, introduces Sen. Bill Nelson, D-Fla., during a news conference on Capitol Hill in Washington, Tuesday, June 21, 2016, to unveil a new gun legislation proposal. From left are Nelson, Sen. Tim Kaine, D-Va., Sen. Martin Heinrich, D-N.M., Sen. Jeff Flake, R-Ariz., and Collins. Evan Vucci AP