The Democratic field is narrowing—but Barack Obama is in no rush to endorse a candidate. CNN, citing sources "close to Obama," report that the former president called Joe Biden, his former vice president, to congratulate him on his big win in the South Carolina primary, but told him that he isn't going to endorse anybody yet. The source says Obama wants to bring the party together, but not until after the primaries are over. "He feels that he's singularly positioned to help unify the party at the end of this," the insider says. "And if he were try to put his thumb on the scale now, it would take away his ability to do so when it's most needed—the general election." The Hill notes that Biden has made his service in the Obama administration a major part of his campaign pitch, and has targeted others, including Bernie Sanders, for criticizing the former president. (More Joe Biden 2020 stories.)