It's a fascinating weakness of this presidency: Mr. Obama has no reliable surrogates. Joe Biden is the vice president, and 90 percent of his job description is to be a carnival barker for his boss. But, particularly since Mr. Biden forced the president's hand on gay marriage, it's apparently dawned on the White House that Mr. Biden is less than dependable as a wingman. Sure, he might begin a statement by saying, "This president saved us from another Great Depression." But you never know if he'll finish by adding, "My neighbor has three rabbits," or, "These are not my pants."