Tennessee Senators Lamar Alexander and Bob Corker are among the targets of a new television ad from Mayors Against Illegal Guns. The spot calls for Senators to support an amendment requiring background checks for all gun sales, even at gun shows and online.

Alexander issued a statement Thursday saying he opposes the measure because he considers it to infringe upon the Second Amendment. Corker has not specified how he intends to vote, but says he “will not support any legislation that violates our Second Amendment rights.”