What does Barack Obama need most in a running mate? Contrary to the conventional wisdom that was echoed during the Democratic primary campaign, Mr. Obama does not necessarily need a female running mate, such as his former rival Hillary Rodham Clinton. The latest Wall Street Journal/NBC News poll indicates that the majority of Democratic women - and the majority of Mrs. Clinton's former supporters - will vote for the Illinois senator in his presidential bid in the fall. Even Hispanics, the majority of whom voted for Mrs. Clinton during the primaries and caucuses, now support Mr. Obama by a margin...