NBC News is asking Mitt Romney's campaign to take down its latest attack ad against Newt Gingrich, which features Tom Brokaw discussing the speaker's ethics violations in a 1997 newscast.

"The NBC Legal Department has written a letter to the campaign asking for the removal of all NBC News material from their campaign ads," Lauren Kapp, a senior vice president in marketing and communications for the company, said in a statement.

Eric...