Is Joe Biden going to be a particular target for Republicans in the months leading up to the November presidential election? It sure looks that way at the moment.

Already this week, Team Romney has accused Mr. Biden of injecting race into the campaign, because he told a largely black audience that the GOP would “put y’all back in chains.” And on Friday, the "super PAC" American Crossroads is releasing an ad that mocks Biden for all manner of verbal slips, from the “chains” remark to his assertion that “jobs” is a three-letter word.