He's not a Cabinet member or an ambassador, but Sen. John Kerry has ascended to the unofficial role of President Obama's global adviser on key issues that could reshape the nation's image around the world. Mediating Afghanistan's presidential election vaulted Mr. Kerry, Massachusetts Democrat, from the already prominent chairmanship of the Senate Foreign Relations Committee into the most exclusive circle around a new president who is juggling but has yet to resolve a variety of domestic and foreign policy matters. Beyond policy, Mr. Kerry knows how Washington works.