Bannon left Breitbart in August 2016 to join Trump's presidential campaign and later served as chief strategist in the White House. He was fired by Trump almost exactly a year after formally signing up with him.
Bannon maintained his visibility by rejoining Breitbart in August and directing it to serve his political ends as the insurgent voice of the "anti-establishment" wing of the Republican Party, a faction that many critics saw as a socially intolerant and racist fringe of white nationalism.
His departure from Breitbart followed what appears to have been a vote of no confidence from a key supporter and investor in the website, Rebekah Mercer, a wealthy political donor, said people at the company who spoke on the condition of anonymity because they were not authorized to speak on Breitbart's behalf. Mercer and her father, hedge-fund billionaire Robert Mercer, own a minority share of Breitbart and are influential voices in its operation.
Bannon provoked Rebekah Mercer's ire by making critical comments about Trump and his family to author Michael Wolff in a book, "Fire and Fury: Inside the Trump White House," published last week. Bannon is quoted as saying that Trump's son, Donald Trump Jr., and son-in-law, Jared Kushner, engaged in "treasonous" behavior by secretly meeting with Russian representatives during the campaign to get unflattering information about Trump's opponent, Hillary Clinton.
Trump replied to Bannon's comments with a statement savaging his former confidant. "Steve Bannon has nothing to do with me or my presidency. When he was fired, he not only lost his job, he lost his mind," the president said. He later attacked Wolff and the book in a tweet in which he referred to Bannon as "Sloppy Steve."
Rebekah Mercer weighed in with a rare statement of her own Thursday that distanced her from Bannon. "I support President Trump and the platform upon which he was elected," she wrote, adding that her family had "not communicated with Steve Bannon in many months and have provided no financial support to his political agenda, nor do we support his recent actions and statements."
Although Bannon continued to chair Breitbart's editorial meetings and host its satellite-radio program, Mercer's comments appeared to signal his end, people at the media company said. Breitbart's readers seemed to side with Trump in the spat.
A person close to Bannon, speaking on the condition of anonymity, said "there is no mass exodus" at Breitbart and people were not entirely surprised by the news.
"It's not personality-driven anymore," the Bannon ally said of the website. "We get to focus on the agenda. When it's about issues, Breitbart wins. We hopefully won't have the cult of personality tearing us down."
Bannon has told associates he plans to focus on creating a political operation in 2018, the person said, and is banking that Trump eventually will need him again and that congressional Republican leaders will eventually desert the president.
It is unclear if he can attract donors or operatives for his operation, though, and the person said that those around Bannon were frustrated by his moves in Alabama and his comments in Wolff's book. White House advisers said that Trump has shown no willingness to forgive him.
As late as last weekend, Bannon continued to tell people that he planned to stay in charge at Breitbart and that he would keep his radio show. He argued that the show and the site were doing better than ever, even though associates have questioned whether that was true. In fact, the radio show would be another casualty of his split with Breitbart. Sirius XM said Tuesday that because its programming agreement was with Breitbart, Bannon would no longer serve as a host.
Even on Tuesday morning, Bannon was preparing for the show, and he invited a friend, longtime political operative Patrick Caddell, to join him on a Wednesday broadcast to talk about immigration. But those plans ended after the announcement. Caddell, in a brief interview, said he was informed late in the day that Breitbart editor Raheem Kassam, not Bannon, would be hosting the Wednesday show. "They said, it'll now be Raheem," he said.
Bannon's ouster came on a day that underscored not only his fade from the power centers of the Republican Party but also his ideology's struggle to gain hold in Congress and at the White House. Trump, who nearly a year ago at his inauguration spoke of "American carnage" and struck nationalist tones, announced Tuesday that he would head to the World Economic Forum in Davos, Switzerland — a gathering Bannon detests — and signaled that he would be willing to work with Democrats on a deal to protect "dreamers," the thousands of children of illegal immigrants, from deportation.
As of Saturday, Bannon was still at Breitbart's Washington headquarters, a Capitol Hill townhouse known as the "Breitbart Embassy." He lives upstairs, while the media operations are based downstairs. During his time in the White House, he told others that he was living in a high-rise building in Rosslyn, Va. It is unclear where he will live now.
As his prospects seemed to cloud in recent days, Bannon grew darkly wistful, two people close to him, who spoke on the condition of anonymity, said. They said he referred to Thomas Cromwell as a historical parallel of sorts to his own experience in private conversations. Cromwell served as the high-profile adviser to King Henry VIII of England in the 16th century but fell out of favor and was executed.
Some conservatives who have worked closely with Bannon were harsh in response, all but writing his political obituary in the hours after the announcement.
"He's gone from the top of the mountain to the deepest valley, and it was all self-inflicted," said veteran GOP strategist Edward J. Rollins, who has worked with Bannon and is chairman of Great America, a pro-Trump group. "Breitbart was his voice and it's been taken away from him, leaving him with nothing."
Former House speaker Newt Gingrich, in a phone call from Rome, where his wife, Callista Gingrich, serves as U.S. ambassador to the Holy See, was withering in his assessment, casting Bannon as a minor player.
"The groundskeeper at the country club didn't do a good job, so the president got a new groundskeeper," Gingrich said, describing Bannon's exit from the White House. When asked if he was calling Bannon a groundskeeper — those who tend to the greens and fairways at golf courses — Gingrich said, "Yes."
"If you decide that you're so important that you can take on the president's daughter, son-in-law, and two sons, and you lose, it has a lot of consequences," Gingrich said.
In a statement carried on Breitbart's website, Bannon said, "I'm proud of what the Breitbart team has accomplished in so short a period of time in building out a world-class news platform."
Bannon declined to comment when reached Tuesday evening.
The Mercers were largely responsible for Bannon's place at Breitbart, and vice versa; Bannon introduced them to the site's founder, Andrew Breitbart, in 2011, and helped persuade them to invest $10 million in Breitbart's vision of an insurgent conservative media outlet that would take on Hollywood, the news media and established Washington figures, including conventional Republicans.
In exchange for their investment, the Mercers secured a seat for Bannon on Breitbart's board. When Breitbart died of a heart condition months later, Bannon took over the operation.
He then set about turning it into a clarion of economic populism and nationalist sentiment. It advocated for strict limits on immigration, particularly from Latin America and from Muslim-majority nations, and for an "America first" agenda in trade. Its political philosophy was amplified by Trump when he announced his candidacy in 2015, although Breitbart steered a relatively even line during the early primaries between Trump and Republican challenger Sen. Ted Cruz (Tex.), the Mercers' preferred candidate.
Bannon, at one point, described Breitbart as "the platform for the alt-right," a phrase that became associated with white separatism, anti-Semitism and generally racist sentiments. Breitbart's editors insisted that the site endorsed none of those views. Nevertheless, Breitbart soared under Bannon, reaching 37 million unique readers a month before Trump won the 2016 presidential election. Among the writers he championed was Milo Yiannopoulos, who elicited both a rapturous response from Breitbart's readers and heavy criticism elsewhere for columns about lesbians, blacks and Muslims.
Following his return to Breitbart, Bannon sought to assert his political muscle by assembling a field of like-minded candidates to challenge incumbents in Republican primaries. His most recent and boldest foray — supporting twice-ousted former judge Roy Moore in the U.S. Senate race in Alabama — turned out to be a disaster.
Moore, accused by several women of preying on them when they were teenagers and he was in his 30s, lost what had been considered a safe seat for Republicans to Democrat Doug Jones.
Yiannopoulos also turned out to be a liability when videos of him appearing to endorse sexual relations between men and teenage boys surfaced in early 2017. Breitbart ended its relationship with him shortly after.
At the same time, Breitbart's business fortunes have been in decline. Monthly traffic has fallen to around 15 million unique readers, according to ComScore, a level that makes Breitbart a leader among conservative news and commentary sites but is far from its election-era peak.
Until very recently, the site had showered Bannon with laudatory coverage, treating him as if he were a leading newsmaker and political philosopher. While most news organizations are reluctant to tell their readers or viewers about their own executives, Breitbart covered Bannon's statements and public appearances religiously. It even covered what other news organizations said about him.
The flattering press notices gave Breitbart the air of a personality cult built around Bannon — all the more so because Bannon was in charge of directing what Breitbart reported.