First he was the self-described “wartime president.” Then he trumpeted the “total” authority of the federal government. But in the past few days, President Trump has nurtured protests against state-issued stay-at-home orders aimed at curtailing the spread of the coronavirus.

Hurtling from one position to another is consistent with Mr. Trump’s approach to the presidency over the past three years. Even when external pressures and stresses appear to change the dynamics that the country is facing, Mr. Trump remains unbowed, altering his approach for a day or two, only to return to nursing grievances.

Not even the president’s re-election campaign can harness him: His team is often reactive to his moods and whims, trying but not always succeeding in steering him in a particular direction. Now, with Mr. Trump’s poll numbers falling after a rally-around-the-leader bump, he is road-testing a new turn on a familiar theme — veering into messages aimed at appealing to Americans whose lives have been disrupted by the legally enforceable stay-at-home orders.

Whether his latest theme will be effective for him is an open question: In an NBC/Wall Street Journal poll released on Sunday, just 36 percent of voters said they generally trusted what Mr. Trump says about the coronavirus.