Retired Army Lt. Col. Alexander Vindman, a key impeachment witness against President Trump, was the "original source" of the Trump-Russia collusion push, not the whistleblower, Fox News contributor Byron York said Wednesday.

York reveals Vindman, who retired from the Army in July after being fired from the National Security Council in February, was the driving force for Democrats' impeachment in his new book, "Obsession: Inside the Washington Establishment's Never-Ending War on Trump."

TRUMP'S TOP ADVISERS WANTED HIM TO FIRE COMEY EARLY ON: BOOK

"It didn't take a real rocket scientist that the source of this, the original source of this, was Lt. Col. Vindman," York told "The Ingraham Angle" Wednesday night, laying out the facts of the case.

"If you remember early on in the Ukraine matter, the Democrats said they wanted the whistleblower to testify, and then they changed their mind and they didn't want the whistleblower to testify and they began to shut off any Republican attempts to find out who the whistleblower was," he said.

Then-National Security Council aide Lt. Col. Alexander Vindman arrives to testify before the House Intelligence Committee on Capitol Hill in Washington, Tuesday, Nov. 19, 2019, during a public impeachment hearing of President Donald Trump's efforts to tie U.S. aid for Ukraine to investigations of his political opponents. (AP Photo/Alex Brandon)

Then-National Security Council aide Lt. Col. Alexander Vindman arrives to testify before the House Intelligence Committee on Capitol Hill in Washington, Tuesday, Nov. 19, 2019, during a public impeachment hearing of President Donald Trump's efforts to tie U.S. aid for Ukraine to investigations of his political opponents. (AP Photo/Alex Brandon)

The Washington Examiner chief political correspondent asked, "So the question is if the whistleblower wasn't in the White House, how did he learn what was going on?"

He points out Vindman was one of several people who listened to Trump's call with Ukrainian President Volodymyr Zelensky, "but [Vindman] was the only one who was disturbed by what took place. He was the only one who thought there was a problem there."

HOUSE DEMS SEEK IG REVIEW OF ALLEGED RETALIATION AGAINST YEVGENY VINDMAN, TWIN BROTHER OF IMPEACHMENT WITNESS

Vindman testified to the Intelligence Committee that he only told two people outside the White House, George Kent, who was a State Department official who specialized in Ukraine, and a member of the intelligence community.

"At that point, Adam Schiff, other Democrats interrupted, you cannot say, you cannot ask the other person he spoke to, and Republicans said well, why can't we ask about that? And they said because it would tend to identify the whistleblower."

Republicans had a "very difficult time handling" Vindman because, although they felt he was the "origin of all this," he was a decorated military officer, York said.

Trump reacted to an excerpt on Vindman in York’s book Thursday.

“No, Vindman knew the call itself to the Ukrainian President was ‘perfect’, but also knew the whistleblower report described the call incorrectly, way off. Why didn’t Vindman say so? That’s why Shifty didn’t want the whistleblower to testify. A big scam!” Trump tweeted.

CLICK HERE TO GET THE FOX NEWS APP

York also claimed former Special Counsel Robert Mueller's team, formed in May of 2017, knew early on there wasn't evidence for Trump-Russia collusion but continued to investigate.

"[Mueller] looked into everything, but what was happening was Trump lawyers could see that Mueller wasn't getting anywhere and by the fall and certainly by the end of the year, they knew that collusion was a dry hole for Mueller," York said. "He had not come up with what he was supposed to find."