Dennis Hastert must report to a federal prison in southeastern Minnesota by Wednesday afternoon to begin serving a 15-month sentence in his hush-money case, one that revealed that the 74-year-old sexually abused at least four boys decades ago when he coached wrestling at a suburban Chicago high school. When he enters the prison gates, the nation's longest-serving GOP speaker, who for eight years was second in the line of succession to the presidency, will be known to prison guards as Inmate No. 47991-424. Hastert pleaded guilty last year to the crime of structuring, which involves withdrawing a large sum of money in small increments to avoid detection. He was taking the money out of his bank accounts to pay compensation for pain and suffering to one of his five sexual abuse victims, he admitted in his plea agreement and at his sentencing hearing. Hastert has not been charged with or convicted of sex abuse due to the statute of limitations, but at his sentencing hearing in April, he admitted to the sexual abuse of boys when he was a high school teacher and coach in his hometown of Yorkville, Ill.