Mr. Bannon, bookish and prone to surrounding himself with like-minded young acolytes, previewed Mr. Trump’s media-bashing during the Thursday session. “They’re corporatist, globalist media that are adamantly opposed — adamantly opposed to an economic nationalist agenda like Donald Trump has,” he said. “I think if you look at the opposition party and how they portray the campaign, how they portrayed the transition and now they’re portraying the administration, it’s always wrong.”

The attacks on the news media come at a time when the press has been reporting on the Trump campaign’s apparent connections to Russia, the botched rollout of Mr. Trump’s executive order on immigration and the forced resignation of Michael T. Flynn, the national security adviser, after less than a month on the job.

“They’re very smart, they’re very cunning and they’re very dishonest,” Mr. Trump said on a day when his press secretary scrapped his daily briefing for an invitation-only off-camera gaggle for selected reporters. The move, people familiar with the situation said, was enthusiastically backed by Mr. Bannon.

The symbiotic political and personal relationship between the two men — the rumpled near-recluse and the compulsively public and image-conscious president — is driving much of the momentum and dysfunction of the White House, aides say.

For all his talk of creating a blueprint for a Trumpian conservatism that outlasts the president’s career, Mr. Bannon is not regarded as a detail-oriented manager, and he let slip during his CPAC appearance that things in the White House have gone well — but only “to the degree we were planning” them.

There is not a lot of daylight between Mr. Trump and Mr. Bannon on the issues, although the president often jokes that Mr. Bannon’s economic populist agenda makes it hard to tell if the former Naval officer and Goldman Sachs executive is “alt-right or alt-left,” according to a Trump associate friendly with both.

The biggest difference between the president and his chief strategist is that Mr. Trump is far less constrained by the dictates of any single philosophy — even Mr. Bannon’s vision of Trumpism — than Mr. Bannon, who sees history as a succession of movements and power struggles.