By Jim Williams

CHICAGO (CBS) — With the presidency, on the line, the impeachment hearing goes public.

And two top diplomats reveal new information about President Trump’s dealings with Ukraine.

CBS 2’s Jim Williams has the story on the historic hearing.

Democrats charge President Trump wanted dirt on a political rival, former Vice President Joe Biden. So they said he extorted Ukraine’s president to get it.

Republicans insisted the Democrats are trying to overturn the 2016 election.

Those arguments opened the impeachment hearings, which featured dramatic testimony from two career diplomats.

The Congressional Committee heard from Bill Taylor, the top American diplomat in Ukraine, and George Kent a senior state department official.

“I’ve served proudly as a non-partisan career foreign service officer for more than 27 years,” Kent said.

Both described what they knew about the central accusation: that President Trump wanted Ukraine’s president to investigate Joe Biden’s son, in exchange for U.S. military aid.

Kent told the lawmakers Mr. Trump’s attorney Rudy Giuliani was pressuring Ukraine.

“In mid-August, it became clear to me that Giuliani’s effort was to gin-up politically motivated investigations were now infecting U.S. engagement with Ukraine, leveraging President Zelensky’s desire for a White House meeting,” Kent said.

President Trump insisted he simply wanted Ukraine to root out corruption. Taylor testified his staff heard from Gordon Sondland, the U.S Ambassador to the European Union, that Mr. Trump’s focus was the Bidens.

“He said he was more interested in the Bidens,” Sondland said.

Republicans repeated their defense of President Trump: whatever he said ultimately it did not affect his support of Ukraine.

“Number one, Ukraine received the aid. number two, there was no investigation into Biden,” said U.S. Representative Elise Sefanik.

“A scheme to condition official acts or taxpayer funding to obtain a personal political benefit does not become less odious because it is discovered before it is fully consummated,” added U.S. Representative Adam Schiff.

At the White House late Wednesday, standing next to the President of Turkey, President Trump said he did not watch one minute of the hearing calling it a witch hunt, a sham and a joke.

The hearings continue Friday.