WASHINGTON _ Stephen K. Bannon helped guide Donald Trump to his upset victory in 2016, then became the president's chief strategist to help remake American politics from inside the White House.
On Tuesday, Bannon spent all day testifying behind closed doors to the House Intelligence Committee, which is probing Russia interference in the U.S. presidential race. It marked the first time Bannon, who was ousted from the White House last August and had an acrimonious falling out with the president this month, was pulled into the multiple investigations that have cast a long shadow over the White House.
But Bannon's next step may be far more significant: He has been subpoenaed to appear before the criminal grand jury working with special counsel Robert S. Mueller III to determine if the Trump campaign assisted the Russian intelligence operation, according to The New York Times.
The president's former senior adviser could provide new details under oath about conversations and meetings inside the Trump campaign and White House at crucial moments, as well as his claims in a new book that Mueller's investigation would be "all about money laundering."
Four former Trump aides, including his former campaign manager Paul Manafort and his former national security adviser, Michael Flynn, already have faced criminal charges. Manafort has pleaded not guilty to fraud, conspiracy and money laundering, and Flynn pleaded guilty to lying to the FBI.
A lawyer for Bannon did not respond to a request for comment Tuesday, and a spokesman for Mueller declined comment on the reported subpoena.
Like his tenure in the White House, Bannon's appearance on Capitol Hill was not short on drama.
Rep. Tom Rooney, a Florida Republican and a member of the panel, said during a break that disagreements about whether Bannon could claim executive privilege to avoid answering some questions were "sort of dominating the day."
Multiple reports said the committee had issued a subpoena to Bannon, an unusual step for a panel that has relied almost exclusively on voluntary interviews with Trump associates and other figures.
Mieke Eoyang, a former committee staff member now at the Washington think tank Third Way, said subpoenas are sometimes used when lawmakers' questions are met with hostility.
"They really don't like it when the witness treats them with contempt," she said. "Everything about Bannon's personality suggests that he wouldn't show the kind of deference and respect that the committee would want from a witness."
White House press secretary Sarah Huckabee Sanders declined to say whether Trump administration officials had asked Bannon to claim executive privilege to protect confidentiality in the White House.
"Congress must consult with the White House prior to obtaining confidential material," she said, reading from a statement. "This is part of a judicially recognized process."
Bannon's testimony has been anticipated since the book "Fire and Fury: Inside the Trump White House," by Michael Wolff, hit the headlines and the bestseller lists this month.
Among other surprises, the book quotes Bannon denouncing a controversial meeting between a Kremlin-linked Russian lawyer and her entourage with three top campaign officials at Trump Tower in June 2016 as "treasonous."
"Even if you thought that this was not treasonous, or unpatriotic, or bad ... and I happen to think it's all of that, you should have called the FBI immediately," Bannon is quoted as saying.
Bannon later backpedaled by saying he was not aiming his barb at Donald Trump Jr., the president's eldest son, who said he had arranged the meeting because he expected the Russians to provide damaging material on Hillary Clinton. Manafort and Jared Kushner, Trump's son-in-law and adviser, also attended.
But Bannon's harsh comments destroyed what was left of his once-close relationship with Trump, who issued a statement saying his former adviser had "lost his mind" when he was forced out of the White House last summer.
The fallout also cost Bannon his job running the right-wing website Breitbart News after his support from major political donors evaporated.
Bannon's testimony comes at a contentious and perhaps critical time for the House Intelligence Committee.
Rep. Adam Schiff of California, the panel's top Democrat, has repeatedly faulted his Republican colleagues for failing to allow a thorough investigation of Russian efforts to meddle in the 2016 presidential campaign through hacking, social media and other tactics.
He's said Republicans have refused to invite dozens of witnesses to testify before the committee and haven't issued some needed subpoenas.
"We can't do a thorough and credible investigation unless we talk to these witnesses and obtain these documents," Schiff said.
Corey Lewandowski, another former Trump campaign manager, is scheduled to testify to the panel behind closed doors Wednesday, according to a source who was not authorized to speak publicly.
Hope Hicks, the White House communications director and a close confidante of the president, also is expected to appear before the panel as soon as this week.
She is likely to be questioned about her role in helping the president craft a misleading response on Air Force One about the June 2016 meeting between the Russian lawyer and the three top campaign officials.
Committee Chairman Devin Nunes, a Republican from California, was forced to step back from the Russia inquiry during a controversy last year over how he had handled classified information.
An ethics committee investigation later cleared him of wrongdoing, and Nunes has aggressively pursued his own lines of inquiry, examining whether the Department of Justice improperly investigated the Trump campaign.
