At 3:45 p.m. on October 6th, 2017, an unassuming man in his early sixties with a low, raspy voice and a thin, wide smile arrived at the White House. He had been here before, in the George W. Bush years, when he was one of the most sought-after fundraisers in the Republican Party. But a scandal had derailed his life, and afterward he had disappeared from politics. In early 2016, the opportunity arose to make his return. The man had helped Donald J. Trump’s long-shot campaign raise millions of dollars, and he could rightly say he played a role in the most improbable presidential victory in American history.