William Taylor, the acting U.S. ambassador to Ukraine, testified Tuesday before the House impeachment inquiry, giving what the Washington Post and a member of the panel call “damning” testimony about President Trump.

In his lengthy opening statement, obtained by the Post, Taylor said “he was told release of military aid was contingent on public declarations from Ukraine that it would investigate the Bidens and the 2016 election, contradicting President Trump’s denial that he used the money as leverage for political gain.”

As expected, Taylor offered details about American officials who apparently joined the effort by Trump and his personal lawyer, Rudy Giuliani, to press Ukraine for investigations of former vice president Joe Biden and his son, Hunter, as well as discredited conspiracy theories that Ukraine meddled in the 2016 U.S. election on behalf of Hillary Clinton.

“Taylor walked lawmakers through a series of conversations he had with other U.S. diplomats” — including Gordon Sondland, ambassador to the European Union — “who were trying to obtain what one called the ‘deliverable’ of Ukrainian help investigating Trump’s political rivals,” the Post says.

Taylor’s statement says that after he arrived in Kiev last spring, he spoke by phone with Sondland, and was told “that President Trump … wants President [Volodymyr] Zelensky to state publicly that Ukraine will investigate Burisma [the gas company that then employed Hunter Biden] and alleged Ukrainian interference in the 2016 election.”

Amb. Sondland also told me that he now recognized that he had made a mistake by earlier telling the Ukrainian officials to whom he spoke that a White House meeting with President Zelensky was dependent on a public announcement of investigations,” Taylor’s statement says, adding that “in fact, Amb. Sondland said, ‘everything’ was dependent on such an announcement, including security assistance.”

It was just the most damning testimony I’ve heard,” Rep. Debbie Wasserman Schultz (D-FL) told the Post in an interview.

He drew a very specific direct line from President Trump to the withholding of foreign aid and the refusal of a meeting,” between Trump and the Ukrainian leader, Wasserman Schultz said, “directly related to both insisting on Zelensky publicly say that he’ll have an investigation, that they will investigate.”

“His memory and recollection seems to be a lot better than Ambassador Sondland’s,” said Rep. Ami Bera (D-CA). Sondland appeared before the committees last week.

Bera, a member of the House Foreign Affairs Committee, told CNN that Taylor was being “candid” and filled in “some gaps” left by previous testimony, but he did not provide details about the closed-door session.

Taylor’s testimony was being closely watched “because of a text message in which he called Trump’s attempt to leverage military aid to Ukraine in return for a political investigation ‘crazy,’” says the Associated Press.

Taylor, a military veteran who served in Vietnam and became a career diplomat, working in both Democratic and Republican administrations, said he warned “several State Department colleagues of a ‘nightmare scenario’ if it came to light” that Trump and his allies tried to pressure Zelensky for political favors by withholding promised military aid.

Taylor’s testimony is the first of two sessions planned by the impeachment inquiry this week.

“Laura Cooper, deputy assistant secretary of defense whose portfolio includes Russia and Ukraine, will testify in a closed session Wednesday, according to an official working on the process,” says the Post.