At today's House Intelligence Committee hearing, FBI Director James Comey will likely undercut President Trump's unsubstantiated claim that President Obama ordered a wiretap of his phones prior to the election, sources familiar with the director's thinking tell ABC News.
Earlier this month, after Comey briefed them privately, the committee's leaders, Republican Chairman Devin Nunes and Democratic Ranking Member Adam Schiff, asserted they have seen "no evidence" to suggest the wiretap occurred.
Comey -- who asked the Justice Department to refute the president's allegations, a move the DOJ declined -- will also discuss alleged Russian interference in the U.S. presidential election and possible connections between Trump associates and the Russian government.
It will be the first time Comey has testified publicly since Trump took office.
But the director's role in the wiretapping controversy is just the latest in a series of notable actions in Comey's long and colorful career.
In November, the director received both praise and criticism for his decision to inform congressional leaders just 11 days before Election Day that investigators were reviewing newly-found emails in connection to the probe of Hillary Clinton’s private email server -- a probe his agency had previously closed.
Comey chose to send the letter despite concerns of U.S. Attorney General Loretta Lynch and other senior Justice Department officials that such a disclosure would go against Justice Department tradition that shied away from making major investigative decisions so close to an election, sources told ABC News.
"In connection with an unrelated case, the FBI has learned of the existence of emails that appear to be pertinent to the investigation," Comey wrote in his letter to lawmakers.
"Of course, we don’t ordinarily tell Congress about ongoing investigations," he wrote in a separate email to FBI employees, noting that in such an important case, he felt it necessary to update Congress and the American people. "In trying to strike that balance, in a brief letter and in the middle of an election season, there is significant risk of being misunderstood, but I wanted you to hear directly from me about it," he said.
The FBI later concluded that the additional emails did not impact the case and Comey told lawmakers he wanted to "supplement the record" so as not to "mislead" the American people.
(Comey had also been criticized in July -- though largely from Republicans -- when he announced that there was no basis for criminal charges against Clinton despite her "extremely careless" handling of emails.)
The towering 6-foot-8 Comey, who served Republican presidents prior to his work for the Obama administration, has never shied away from controversy.
How He Became One of America's Top Cops
President George W. Bush appointed Comey deputy attorney general in 2003, at the height of tough legal questions surrounding the war on terror and the Patriot Act. Prior to that, he served as the top federal prosecutor in New York City, where he took on a number of major terrorism and criminal cases.
"He is known as a straight shooter and fairly non-partisan, which is reflected in the fact that he was confirmed for his current position as FBI director by 93-1 vote [in the Senate],” ABC News senior legal analyst Sunny Hostin said.
His High-Profile Case Load and a Bedside Drama
Over the course of his career, Comey, 55, has been involved in a number of blockbuster cases. He prosecuted businesswoman Martha Stewart and mobster John Gambino, and handled the investigation and indictments of the suspects in the Khobar Towers bombing in Saudi Arabia. He appointed the special investigator to lead the probe into the leaking of CIA officer Valerie Plame's name, a politically charged inquiry that resulted in the conviction of Vice President Dick Cheney's adviser Scooter Libby.
And, most famously, Comey reportedly rushed to John Ashcroft's hospital bedside in 2004 to stand up to White House officials who were allegedly trying to obtain an extension of a controversial warrantless wiretapping program from the attorney general. Ashcroft had been hospitalized after gall bladder surgery, and Comey was serving as the acting A.G. in his place and had refused to extend the program.
"Jim always demonstrated great integrity and political independence from the White House, even if it made him unpopular," John Bellinger, former legal adviser to the National Security Council during the Bush Administration, told ABC News.
His Connection to the Clintons Prior to the 2016 Election
Comey's past head-to-head encounters with presidential administrations perhaps made him uniquely qualified to oversee the investigation into Clinton’s controversial email practices, and it was not the first time he weighed in on matters relating to the Clinton’s. In 1996, Comey served as deputy special counsel to the Senate special committee on the Whitewater investigation, chaired by Republicans at the time, which linked Hillary Clinton to the mishandling and destruction of documents.
Comey was also involved at both ends of the case of Marc Rich, a billionaire oil trader indicted for tax fraud and trading with Iran during the hostage crisis, who was later pardoned by President Bill Clinton during his final day in office in 2001. In a letter to the Senate, Comey describes working as both the lead prosecutor in New York on the original case against Rich in 1983 and then later, in 2002, overseeing criminal investigations into Clinton's last-minute pardons.
The investigations concluded there was no wrongdoing on the president's part, despite public outcry over evidence that Rich's ex-wife had donated to Hillary Clinton's Senate campaign.