WASHINGTON — President Trump once said “I alone can fix it.” Looks like he may have to. No one else seems to be sticking around.

The record-high turnover at the White House has now reached 43 percent with the pending departure of Gary D. Cohn, the national economic adviser, as the team that arrived with Mr. Trump 13 months ago heads for the doors in increasing numbers and the president increasingly relies on his own judgment for key decisions.

The head-spinning pace of departures has contributed to the sense of disarray in the West Wing, but it reflects the way Mr. Trump has operated since he announced that he was running for president. He constantly searches for new voices, but burns through staff as he quickly loses faith in the people around him, leaving him with a dearth of advisers on whom he genuinely depends. In effect, it can feel like a presidency of one.

Mr. Trump said this week that this did not lead to chaos but to a healthy refreshing of his team, adding that a reasonable amount of conflict helped him make better decisions. But Washington veterans see a dysfunctional operation in which a president becomes trapped in an insular bubble and too dependent on his own instincts and assessments, however informed they may or may not be.