Dr. Hill said she had told Mr. Sondland at the time that, “this is all going to blow up.”
Mr. Holmes said it was his “clear understanding” by the end of August that Mr. Trump had frozen $391 million in vital security aid to pressure Ukraine to commit to announcing an investigation into Mr. Biden and his family.
Their testimony came as Democrats sought to pull back the focus of the impeachment proceedings at the end of two weeks of detail-heavy hearings focused on White House meetings, suspended security assistance for Ukraine, diplomatic exchanges and plenty of obscure Ukrainian names. But they also notched additional new information that could help bolster their case.
Republicans, knowing that Dr. Hill’s criticism was coming, used their opening remarks to try to blunt the attacks. Representative Devin Nunes of California, the panel’s top Republican, said that his party did not doubt Russia’s actions in 2016, but were open to a broader focus that Democrats were not.
“Needless to say, it’s entirely possible for two separate nations to engage in election meddling at the same time, and Republicans believe we should take meddling seriously by all foreign countries,” Mr. Nunes said.
In 2017, American intelligence officials released a report concluding that Mr. Putin ordered a state-sponsored campaign to try to influence the 2016 presidential election. No evidence has emerged that there was a similar effort by Ukraine.
Mr. Trump, who has responded to the proceedings in real time, took shots at Mr. Holmes Thursday morning, and his allies went after Dr. Hill as well. As Mr. Holmes testified, Mr. Trump wrote on Twitter that there was no way he could have heard what he claimed to have picked up the cellphone conversation between Mr. Trump and Mr. Sondland.
Donald Trump Jr., the president’s eldest son, wrote on Twitter that Dr. Hill only had an “OPINION” to offer, not firsthand knowledge. Republicans have dismissed multiple witnesses as unelected bureaucrats merely second-guessing the president’s policy positions.