Bernie Sanders, previously known for his aversion to negative attacks on opponents, called on Hillary Clinton to apologize for 2008 anti-Obama ad.

Sanders tweeted, "Maybe Hillary Clinton should apologize for this?"

Attached is a link to a 2008 mailer at the height of the Democratic primary campaign that Clinton eventually lost calling out Obama's record on gun control.

Sanders has been similarly faulted for his gun control record by Clinton, though it is unclear if Obama ever actually voted against a gun control measure.

The Clinton mailer faults Obama because, "he was for the 2nd Amendment, in order to get votes." No Democratic candidate has explicitly advocated repealing the Second Amendment.