Democratic representative Stephen Lynch, a senior member of the House oversight and reform committee, was quoted in Politico as saying the testimony was a “sea change” that “could accelerate” the impeachment inquiry.
New Jersey representative Tom Malinowski, a Democrat, said it was “the most thorough accounting we’ve had of the timeline”.
Taylor had flown to Washington in response to a congressional subpoena and in defiance of an administration gag order.
The Politico website quoted a source in the private briefing as saying Taylor’s opening statement was 15 pages long and prompted “a lot of sighs and gasps”.
Taylor was brought out of retirement in June after the former ambassador to Kyiv, Marie Yovanovitch, was abruptly removed from her post.
In diplomatic texts released by Congress, it is Taylor who most clearly expresses the quid pro quo being presented to the Ukrainian government by Trump’s emissaries, and his deep concern about it.
“I think it’s crazy to withhold security assistance for help with a political campaign,” Taylor wrote on 9 September to Sondland.
Trump suspended $400m in military aid to Ukraine a few days before a 25 July phone call to Zelenskiy. In the released version of the call, when the Ukrainian president raised the matter of US military support Trump responded: “I would like you to do us a favour though… …”
Trump then asked for the investigations.
Before taking up his post, Taylor requested a meeting with secretary of state Mike Pompeo to seek reassurance about administration support for Ukraine.
“I made clear to [Pompeo] and the others president, that if US policy towards Ukraine changed, he would not want me posted there and I could not stay,” Taylor’s opening statement on Tuesday said. “He assured me that the policy of strong support for Ukraine would continue.”