WASHINGTON — Acting U.S. ambassador to Ukraine Bill Taylor added one more bombshell to his explosive timeline of President Trump’s efforts towards Ukraine: An overheard call where Trump asked about the “investigations” into Joe Biden and his family.

Taylor says he was told by a staffer last Friday that they were with U.S. Ambassador to the European Union Gordon Sondland when he called President Trump on July 26, just one day after Trump’s now-famous call with Ukraine President Volodymyr Zelensky.

The staffer overheard Trump ask Sondland about “the investigations” — and that Sondland made clear afterwards what exactly Trump was asking about.

“In the presence of my staff at a restaurant, Ambassador Sondland called President Trump and told him of his meetings in Kyiv. The member of my staff could hear President Trump on the phone, asking Ambassador Sondland about ‘the investigations.’ Ambassador Sondland told President Trump that the Ukrainians were ready to move forward,” Taylor said.

“Following the call with President Trump, the member of my staff asked Ambassador Sondland what President Trump thought about Ukraine. Ambassador Sondland responded that President Trump cares more about the investigations of Biden, which Giuliani was pressing for,” Taylor said.

That allegation is crucial — it suggests that Trump pushed directly for an investigation into the Bidens, a question at the heart of the impeachment investigation.

Surprise witness

Moments after Taylor’s surprise revelation of the Trump-Sondland restaurant phone call, a new witness deposition was announced for this Friday from a staffer working for Taylor at the U.S. embassy in Ukraine.

The impeachment committees will hear closed-door testimony from David Holmes, the embassy’s counselor for political affairs.

Taylor said he understood that the committee is “following up on this matter.” A spokesperson for the House Intelligence Committee declined to comment when asked whether Holmes is the staffer Taylor was referring to in his testimony.

Taylor’s allegation came during the first public testimony of the House impeachment inquiry, a key moment as Democrats move to lay our their arguments for why Trump should be removed from office.

The crux of their argument: That Trump sought to extort Ukraine’s leaders into publicly announcing investigations into the Bidens and the 2016 election by withholding congressionally approved military aid from the country.