Passing the 1994 assault weapons ban cost more than a dozen Democrats their seats in the 1994 midterm elections.  In fact, according to former President Bill Clinton, then-Speaker of the House Tom Foley (D-Wash.) lost his election because of the misguided law.

http://www.politico.com/story/2013/01/bill-clinton-to-democrats-dont-trivialize-gun-culture-86443.html