As the impeachment inquiry moves into a critical week, President Trump and his Republican allies are debating the degree to which the president should participate in a process they have spent Four constitutional scholars — three chosen by Democrats, one by Republicans — are expected to testify on the standards for impeachment. Nadler (D-N.Y.) told Trump he had until 6 p.m. Sunday to notify the committee that he or his attorneys would attend; he has given Trump until Friday to decide whether to participate more broadly in the impeachment process.