Originally posted by the Voice of America. Voice of America content is produced by the Voice of America, a United States federal government-sponsored entity, and is in the public domain. Ex-White House Aide Balks at Impeachment Inquiry Testimony Ken Bredemeier WASHINGTON - A former White House national security aide balked Monday at testifying in the ongoing Democratic-led impeachment inquiry targeting President Donald Trump. Charles Kupperman, who served as a deputy to former national security adviser John Bolton, had been subpoenaed by Democratic lawmakers in the House of Representatives to answer questions behind closed doors about any knowledge he has about how Trump pressured Ukraine to open investigations to help him politically. Kupperman listened in on the July 25 call in which Trump pushed Ukrainian President Volodymyr Zelenskiy for "a favor" -- to investigate any involvement the country had in the effort to defeat him in the 2016 election and to investigate one of Trump's chief Democratic rivals in the 2020 election, former Vice President Joe Biden, and his son Hunter Biden's lucrative job as a one-time board member for Burisma, a Ukrainian natural gas company. The call, which Trump has described as "perfect," is at the center of the impeachment inquiry. References Visible links Hidden links: 1. file://localhost/episode/how-impeachment-inquiry-affects-american-politics-4056146 .