But Tim Morrison, the top Russia official on President Trump's National Security Council, said he found nothing wrong with the July 25 call between the U.S. president and his Ukrainian counterpart.
House Speaker Nancy Pelosi warned the president not to intimidate the whistleblower, as the president continued to call for the anonymous person to be exposed.
The former defense secretary, who has been accused of human rights abuses during the country's civil war, campaigned on a platform of stability and national security.
The Attorney General's remarks at The Federalist Society drew swift criticism from some legal experts, who decried his ideas as "authoritarian" and "dangerous."
In Saturday's race, Gov. John Bel Edwards, the Louisiana Democrat, was able to defeat Republican Eddie Rispone, who President Trump heartily endorsed.
Former U.S. Ambassador to Ukraine Marie Yovanovitch testified before Congress on the second day of public hearings in the House impeachment inquiry into President Trump.
At the time of her deposition on Nov. 7, her lawyer told NPR that Williams's testimony "will largely reflect what is already in the public record."
In his closed-door deposition on Oct. 31, Morrison said President Trump had indeed asked Ukraine's president for assistance, but he argued the president's conduct wasn't unlawful.
David Holmes, the State Department official who overheard a phone call between the president and a top diplomat, appeared in a closed-door deposition Friday before the House impeachment inquiry.
Closed-door testimony from the only White House staffer cooperating with the probe could provide first-hand knowledge about details that remain hazy.
The former U.S. Ambassador to Ukraine, Marie Yovanovitch, testified in front of the House Intelligence Committee on Friday in the public phase of the impeachment inquiry.
Read an annotation of the complaint that set off the formal impeachment inquiry in the House of Representatives, with references to congressional testimony, public statements and news reports.