President Trump decided to dismiss Stephen K. Bannon, after weeks of White House upheaval and racial unrest. The ousted chief strategist returned to Breitbart News on Aug. 18. (Peter Stevenson,Jenny Starrs/The Washington Post)

Stephen K. Bannon caused trouble in the White House. He could have even more of an impact on the outside.

President Trump has decided to remove his chief strategist following a tumultuous week, even by the standards of this White House. Trump drew criticism from within his party for a take on violence in Charlottesville that bore the fingerprints of Bannon and Breitbart News, the website Bannon once chaired and called “the platform for the alt-right.”

On top of that episode, Bannon phoned a journalist at the American Prospect, unsolicited, and undercut the president's public stance that all options are on the table in a standoff with North Korea. “There’s no military solution,” Bannon said. “Forget it.”

Under different circumstances, the latter might have been a fireable offense, automatically. Trump rails against leaks that reveal internal disagreements, and here was Bannon going on the record about national security deliberations and contradicting the commander in chief.

But Bannon came to the White House marked “handle with care.” He represents the cornerstone of Trump's base — the populist, nationalist wing of the Republican Party that latched on to the fiery billionaire long before others in the GOP.

If a bitter Bannon were to return to the media and spread disillusionment among Trump's followers, he could become a problem for the president. Breitbart alum Ben Shapiro predicted a fierce battle.

Trump does have a knack for keeping former aides on his side. Roger Stone and Corey Lewandowski are prime examples of people who have devoted themselves to boosting the president in the media after leaving his service.

If Trump can manage another amiable split, perhaps Bannon will remain a valuable ally. The Washington Post's Ashley Parker, Philip Rucker, Robert Costa and Damian Paletta reported Friday that “Bannon had been expecting to be cut loose from the White House, people close to him said, with one of them explaining that Bannon was resigned to that fate and is determined to continue to advocate for Trump’s agenda on the outside.”

Bannon wouldn't necessarily have to pull a complete reversal to give Trump a headache, however. He could focus his fury on former White House rivals who pulled the president in different directions. Even that kind of narrative would crack Trump's image as a swashbuckling Washington outsider determined to “drain the swamp.”

Bannon certainly would have plenty to complain about. As Trump's posture on North Korea illustrates, the president is not governing as the noninterventionist he played on the campaign trail. He has supported Republican health-care plans that fall short of the full Obamacare repeal he promised as a candidate, and he has made little tangible progress on a southern border wall.

Breitbart News, though loyal to Trump, has criticized him on these issues.

Although it is possible that Bannon could return to Breitbart, he also could launch a new venture. That's what media entrepreneur Jim VandeHei predicted before news of Bannon's departure broke.

One other potential drawback for Trump: Bannon was useful, at times, as a shield. The president's critics sometimes suggested that Bannon, not Trump alone, was responsible for political missteps.

Bannon himself seemed to embrace the role, telling the Daily Mail on Thursday that his call to the American Prospect “drew fire away” from Trump.

Robert Kuttner, co-editor of the American Prospect, got an unexpected interview with White House chief strategist Stephen K. Bannon on Aug. 15. (Peter Stevenson/The Washington Post)