The top US diplomat in Ukraine, Bill Taylor, on Wednesday revealed new information in his opening statement, testifying at the first House impeachment hearing that his staff was told the President’s interest in Ukraine was the “investigations of Biden.”

Taylor testified that an aide told him of a phone conversation Trump had with US Ambassador to the European Union Gordon Sondland on July 26, one day after Trump’s phone call with Ukrainian President Volodymyr Zelensky. Taylor’s aide, who was accompanying Sondland to meetings in Kiev with Ukrainian officials, could hear Trump asking Sondland about the investigations, Taylor testified. Sondland “told President Trump that the Ukrainians were ready to move forward,” Taylor said.

Taylor testified that his aide later asked Sondland what Trump thought of Ukraine.

“Ambassador Sondland responded that President Trump cares more about the investigations of Biden, which (Trump personal attorney Rudy) Giuliani was pressing for,” Taylor said.

The House is taking a historic step forward Wednesday in its impeachment inquiry of Trump with public hearings that Democrats hope will show the public that the President abused the power of his office to obtain dirt on a potential 2020 rival while withholding vital security aid from Ukraine.

Taylor and Deputy Assistant Secretary of State George Kent are testifying at the hearing. Both received subpoenas Wednesday to testify, according to an official working on the impeachment inquiry, which also were issued before their closed-door depositions last month.

Taylor is one of the most important witnesses for the Democrats impeachment case. He testified behind closed doors last month that he was told Trump held up US security aid and denied a one-on-one meeting with the Ukrainian President unless Ukraine announced an investigation into his political rivals. Taylor said he was told by officials who spoke with the President that Trump wanted Zelensky to “go to a microphone” to announce the investigation.

Last month, Kent told lawmakers in his closed-door deposition that Giuliani was part of a “campaign of lies” in Ukraine that led to the ouster of US Ambassador to Ukraine Marie Yovanovitch and then the push for investigations.

In his opening statement, Kent defended Yovanovitch and other US diplomats who have come under attack, adding that Giuliani’s shadow efforts “hampered US efforts to establish rapport with the new Zelensky administration.”

“In mid-August, it became clear to me that Giuliani’s efforts to gin up politically-motivated investigations were now infecting U.S. engagement with Ukraine, leveraging President Zelensky’s desire for a White House meeting,” Kent said.

House Intelligence Chairman Adam Schiff, a California Democrat, said in his opening statement that the impeachment inquiry will seek to answer whether Trump invited Ukraine’s interference in US elections, whether Trump conditioned a White House meeting and US aid on announcing political investigations and “if President Trump did either, whether such an abuse of his power is compatible with the office of the presidency?”

“The matter is as simple, and as terrible as that,” Schiff said. “Our answer to these questions will affect not only the future of this presidency, but the future of the presidency itself, and what kind of conduct or misconduct the American people may come to expect from their Commander-in-Chief.”

A Democratic aide said Taylor and Kent were paired together because they were able to provide the “full timeline” of the President’s actions in Ukraine.

Rep. Devin Nunes, the ranking Republican on the Intelligence Committee, accused Democrats of undertaking a “scorched-earth war against President Trump,” saying they were using a “carefully orchestrated media smear campaign” to impeach the President.

“What we will witness today is the theatrical performance,” Nunes said.

Republicans are expected to use the hearing to try to undercut the Democrats’ impeachment arguments. They released an 18-page memo pushing back on the Democrats’ case, arguing that both Trump and Zelensky say there was no pressure and the aid money was released without any investigation. Republicans have also argued that Taylor’s charges against the President are only based on second- and third-hand information.

The public portion of the impeachment inquiry continues Friday with the testimony of former US Ambassador to Ukraine Marie Yovanovitch. The Intelligence Committee has scheduled eight witnesses to appear at public hearings next week.