Amna Nawaz:

All of this as President Trump's other critical challenge ground on, with another key witness testifying in the impeachment inquiry.

Michael McKinley, a senior adviser to Secretary of State Mike Pompeo, abruptly resigned from his post last week. He was reportedly telling congressional investigators that his departure was driven by a concern over the treatment of former Ambassador to Ukraine Marie Yovanovitch. She was recalled from her post in May, amid agitation inside the White House that she was disloyal to the president.

Also on the Hill today, a surprise second appearance from former U.S. envoy to Ukraine Kurt Volker. State Department official George Kent told lawmakers yesterday that Volker was part of a group that took over the administration's Ukraine policy.

Democratic Congressman Gerry Connolly said the group also included Gordon Sondland, the U.S. ambassador to the European Union, and Energy Secretary Rick Perry. They allegedly dubbed themselves the three amigos.

With back-to back interviews and depositions this week, House Democrats are pushing on with the probe, even as Speaker Nancy Pelosi said yesterday the House would hold off on a vote to formally authorize the inquiry.

Today, House Republicans again accused Democrats of running an unfair process. House Minority Leader Kevin McCarthy said they are being denied access to closed testimony and transcripts.