The acting U.S. ambassador to Ukraine on Wednesday offered new information about President Donald Trump’s interest in having the country investigate Trump’s political rivals, as a House committee kicked off the first open impeachment hearings.

Facing a panel of lawmakers, William Taylor said Trump spoke with U.S. Ambassador to the European Union Gordon Sondland on July 26 about “the investigations.” That conversation came a day after Trump’s phone call with Ukrainian President Volodymyr Zelensky, in which Trump asked for probes of former Vice President Joe Biden and his son, and the 2016 presidential election in the U.S. Taylor said he was told about the July 26 conversation by an aide.

The diplomat’s testimony came after House Intelligence Committee Chairman Adam Schiff opened the hearing by warning that the presidency is at stake, as Democrats mark a new and dramatic phase of the probe into alleged wrongdoing by Trump.

“There are few actions as consequential as the impeachment of a president,” said Schiff, a California Democrat, in an opening statement. Rep. Devin Nunes, the committee’s top Republican, called the impeachment inquiry a “publicly orchestrated media smear campaign” in his opening remarks.

The panel heard testimony from Taylor and George Kent, a senior State Department official.

As Democrats investigate whether Trump abused his power by withholding aid to Ukraine to pressure that country, the U.S. president has denied wrongdoing and furiously attacked Democrats and public officials. On Wednesday morning, Trump tweeted, “Never Trumpers!” That’s a label he’s applied to Taylor and other officials despite lack of evidence of any political bias.

Speaking to reporters alongside visiting Turkish President Recep Tayyip Erdogan, Trump said, “It’s a witch hunt, it’s a hoax. I’m too busy to watch it. I have not been briefed.”

Trump later said he knew “nothing” about the call that was detailed by Taylor on Wednesday. “First time I’ve heard it,” he said at a news conference with Erdogan.

Trump has described as “perfect” the July 25 phone call in which he asked Zelensky to investigate Joe Biden and his son Hunter. He again Wednesday urged his Twitter followers to read what the White House calls a transcript of the call — which is not a verbatim document. (See summary of Trump-Zelensky call as released by the White House.)

During a question-and-answer period, Nunes attempted to turn the hearing’s focus back to alleged Ukrainian meddling in the 2016 election. That view is outside of U.S. intelligence findings.

Democrats “downplay, ignore or outright deny the many indications that Ukrainians actually did meddle in the election,” Nunes said. Trump’s first homeland-security adviser, Thomas Bossert, told ABC’s “This Week” in September that he had told Trump there was no basis to the theory that Ukraine — and not Russia — intervened in the 2016 election, and that the country did so on Democrats’ behalf.

The hearings came a week before Biden and other Democratic presidential hopefuls meet for their next debate. With the 2020 campaign intensifying and the first public impeachment hearings getting under way, polls showed more than half of Americans supported beginning the impeachment process — but under half supported Trump’s impeachment and removal.

The impeachment hearings competed for investors’ attention on Wednesday with a Capitol Hill appearance by Federal Reserve Chairman Jerome Powell.

U.S. stocks SPX, +1.59% DJIA, +1.33% rose as Washington and Wall Street divided their attention between impeachment and the Fed chief. Both the Dow Jones Industrial Average and S&P 500 index closed at new records, as a five-week rally rolled on.

Read:Powell signals pause unless there is material change in outlook: Live blog recap

Also see:Stocks at record heights even as Trump impeachment enters a new phase — here’s why

On Friday, former U.S. Ambassador to Ukraine Marie Yovanovitch is scheduled to testify. She is expected to describe the push to oust her from her post.

An impeachment vote is expected in the Democratic-led House next month, with a Senate trial to follow, likely in January. The Republicans who control the Senate, however, are not considered likely to back Trump’s removal from office.

Also see: Mulvaney won’t sue over impeachment inquiry, will instead refuse to cooperate