Vice President Joseph R. Biden's incendiary comment to a largely black audience Tuesday about Republican Mitt Romney wanting to put voters "back in chains" isn't the first time he has used slavery imagery in a political appeal.

In 2006, when then-Delaware senator was campaigning in South Carolina for the 2008 Democratic presidential nomination, he reminded people that he represented a former slave state.

Asked on Fox News how a "Northeast liberal" such as himself could win in South Carolina, Mr. Biden replied, "You don't know my state. My state was a slave state. My state is a border state. My state is the eighth largest black population in the country. My state is anything from a Northeast liberal state."...