CAPITOL HILL - House Democrats will launch a new phase in the impeachment investigation of U.S. President Donald Trump next week with a round of public testimony from former administration officials. Those witnesses will provide a detailed picture of Trump’s alleged invitation of foreign interference into the 2020 presidential election. Newly released transcripts from the closed door testimony preview could mark a pivotal week in the Trump presidency.

Weeks of witness testimony behind closed doors on Capitol Hill are about to go public. House Intelligence Committee Chairman Adam Schiff is leading the open hearings that Democrats hope will make a case to the American people for the impeachment of President Trump.

Former Ambassador William Taylor leaves a closed door meeting after testifying as part of the House impeachment inquiry into President Donald Trump, on Capitol Hill in Washington, Oct. 22, 2019.

The first to testify will be one of the Democrats’ key witnesses, Ambassador William Taylor. Schiff expressed his support for Taylor.

“Someone who is I think performing another vital service for the country in relating the facts that came to his attention — the very disturbing facts that came to his attention,” Schiff said.

Taylor, the top U.S. diplomat to Ukraine, has already told House lawmakers it was clear U.S. security assistance to Ukraine was tied to that country’s cooperation in an investigation into Trump’s political rival, former Vice President Joe Biden and Biden's son, Hunter.

Also testifying next week, State Department official George Kent and former U.S. Ambassador to Ukraine Marie Yovanovitch, who will tell lawmakers of efforts to subvert traditional U.S. foreign policy channels in favor of Rudy Giuliani, the president’s personal lawyer.

Republicans say the president’s call with Ukrainian President Volodymyr Zelinskiy should be the focus.

FILE - Ukraine's President Volodymyr Zelenskiy and U.S. President Donald Trump face reporters during a bilateral meeting on the sidelines of the 74th session of the United Nations General Assembly in New York, Sept. 25, 2019.

“I trust the call. I trust President Zelenskiy and President Trump. And I trust the fact that the Ukrainians didn’t know that aid had been held and the Ukrainians did nothing to get it released, when it was released. Those are the fundamental facts, but we got all this, all this, other noise that Mr. Schiff wants to stir up that isn’t fundamentally critical to what actually took place,” Jordan said.

Trump has called the House impeachment process unfair.

“They shouldn’t be having public hearings. This is a hoax. This is just like the Russian witch hunt,” Trump said.

House Democrats are following a similar process used in the impeachment inquiries of Presidents Richard Nixon and Bill Clinton, said Brookings Institution analyst Elaine Kamarck.

“The impeachment process, at this point in time, is like a grand jury process. What they're doing now is they're just gathering evidence. They're going to make charges. And obviously House Republicans will have the chance to rebut the charges,” Kamarck said.

Charges in the form of articles of impeachment could come as early as December and would almost certainly pass the Democratic-controlled House of Representatives. The resulting trial in the Republican-majority Senate would likely not be successful — keeping Trump in office.