There was no talk of joining the Taliban when Afghan President Hamid Karzai sat down Thursday afternoon for a “public conversation” with Secretary of State Hillary Rodham Clinton. The threat Mr. Karzai issued recently in a pique of frustration over US pressure on him and his country seemed to be buried and gone. Instead, during three days in Washington, the Afghan leader basked in his new role as a crucial and trusted partner of the United States – firmly rehabilitated from the times when the Obama administration hinted that he was a corrupt and ineffective leader. Over the course of his one-hour appearance with Secretary Clinton at the US Institute of Peace in Washington, Karzai’s suave performance suggested how that rehabilitation had been won. He spoke to an audience that included President Obama’s special envoy for Afghanistan and Pakistan, Richard Holbrooke, as well as some members of Congress and Washington think-tankers.