A view of the U.S. Capitol this month. House investigators are expected to press Charles Kupperman, deputy to then-National Security Adviser John Bolton, to corroborate key elements of an account that President Trump built a shadow foreign policy team to pressure the Ukrainian president.

A view of the U.S. Capitol this month. House investigators are expected to press Charles Kupperman, deputy to then-National Security Adviser John Bolton, to corroborate key elements of an account that President Trump built a shadow foreign policy team to pressure the Ukrainian president.