evidence: Nineteen of the 22 living former presidential chiefs of staff, some of the biggest personalities in Washington over the past five decades, arrived to support Ronald Alan Klain, a man whose shoulders would soon bear the weight of Washington's most unforgiving job. Klain, the Indiana native and veteran of all three branches of government and K Street, had been training for the job of President Joe Biden's chief of staff since he was a child. [...] Klain's presidential commission — an oversized official piece of paper signed by Biden making him an officer and chief of staff — begins: "Ronald Alan Klain of Indiana." [...] Klain's approach to the job focuses more on "staff" than "chief," those who work with him say. "Because he has grown up as a staff person, he is a staffer's chief of staff," said Elizabeth Alexander, who worked with Klain when she was Biden's press secretary during his vice presidency and is now Jill Biden's communications director.