The 2020 Democratic candidate with whom the CIA whistleblower had a "professional" tie is Joe Biden, according to intelligence officers and former White House officials.

Lawyers for the whistleblower said he had worked only "in the executive branch." The Washington Examiner has established that he is a career CIA analyst who was detailed to the National Security Council at the White House and has since left. On Sept. 26, the New York Times reported that he was a CIA officer. On Oct. 4, the newspaper added that he "was detailed to the National Security Council at one point."

Michael Atkinson, the Intelligence Community's inspector general, told members of Congress that the whistleblower had a "professional tie" to a 2020 Democratic candidate. He had written earlier that while the whistleblower's complaint was credible, he had shown "some indicia of an arguable political bias ... in favor of a rival political candidate."

A retired CIA officer told the Washington Examiner, “From everything we know about the whistleblower and his work in the executive branch then, there is absolutely no doubt he would have been working with Biden when he was vice president."

As an experienced CIA official on the NSC with the deep knowledge of Ukraine that he demonstrated in his complaint, it is probable that the whistleblower briefed Biden and likely that he accompanied him on Air Force Two during at least one of the six visits the 2020 candidate made to the country.

A former Trump administration official, speaking on condition of anonymity to discuss intelligence matters, said Biden’s work on foreign affairs brought him into close proximity with the whistleblower either at the CIA or when he was detailed to the White House.

“This person, after working with Biden, may feel defensive towards him because he feels [Biden] is being falsely attacked. Maybe he is even talking to Biden’s staff,” the former official said. “Maybe it is innocent, maybe not.”

Last month, the whistleblower accused President Trump of abusing his position by asking Ukrainian President Volodymyr Zelensky to investigate Biden and his son, Hunter, who sat on the board of a Ukrainian gas company. His complaint is now at the center of a Democrat-led impeachment inquiry, prompting Trump and his allies to cry foul.

Biden was President Barack Obama’s "point man" on Ukraine, making a half dozen trips there in his eight years as vice president. Those trips involved briefings from senior intelligence officials and NSC officers, some of whom traveled with him to Kyiv and elsewhere.

“The Whistleblower has ties to one of my DEMOCRAT OPPONENTS,” tweeted Trump, after the "professional" link was revealed by the Washington Examiner. “Why does the ICIG allow this scam to continue?”

The Whistleblower’s facts have been so incorrect about my “no pressure” conversation with the Ukrainian President, and now the conflict of interest and involvement with a Democrat Candidate, that he or she should be exposed and questioned properly. This is no Whistleblower..... — Donald J. Trump (@realDonaldTrump) October 9, 2019

Trump said Thursday he did not know the identity of the whistleblower.

The connection to Biden has emerged a week after Atkinson, the Intelligence Community's inspector general, briefed the House Intelligence Committee on the whistleblower’s complaint.

After the report on what Atkinson said, lawyers for the whistleblower immediately insisted their client was not motivated by political considerations, but their cryptic comment fueled speculation about his identity. The careful statement did not rule out that the whistleblower worked with one of the candidates before they started running for president.

"First, our client has never worked for or advised a political candidate, campaign, or party," said Andrew Bakaj and Mark Zaid. "Second, our client has spent their entire government career in apolitical, civil servant positions in the Executive Branch."

4/Third, in these positions our client has come into contact with presidential candidates from both parties in their roles as elected officials—not as candidates. — Mark S. Zaid (@MarkSZaidEsq) October 9, 2019

Glenn Carle, a former CIA officer who himself blew the whistle on George W. Bush administration efforts to collect intelligence on an American citizen, said the distinction was crucial. “The truth is that the whistleblower would have worked with Biden not in some partisan political sense but as a member of the government,” he said. “It is scurrilous to suppose there was a political motivation.”

He added that it was possible that the CIA officer briefed senators or representatives who were now running for president.