Some State Department officials have resorted to back channels to voice their complaints, congressional aides said. Over the summer, as confidence in Mr. Pompeo eroded, a stream of career officials spoke quietly with congressional offices about their concerns over administration policy — on the hold on Ukraine military aid, a move to cut $4 billion of foreign aid, and arms sales to Saudi Arabia and the United Arab Emirates.

On Oct. 23, the three congressional impeachment committees said Mr. Pompeo had overseen a “culture of harassment and impunity.” That echoed what Ms. Yovanovitch had told investigators: The State Department was being “attacked and hollowed out from within,” she said.

In interviews on Oct. 30 with Fox News and The New York Post, two of Mr. Trump’s favorite media organizations, Mr. Pompeo pushed a new conspiracy theory involving Mr. Biden’s son and President Barack Obama’s policy of military aid to Ukraine — a theory that career officials under him find outlandish.

“Pompeo has consistently demonstrated that the only safe place on Trump’s foreign policy team is to be more Trumpian than the president himself,” said Andrew Weiss, a former official with the White House National Security Council, the State Department and the Pentagon in Democratic and Republican administrations. “Whether that means trafficking in over-the-top partisan attacks on Trump’s opponents or conspiracy-mongering about the 2016 election and the Ukraine scandal, he’s always willing to go there.”

“It seems that the only thing Pompeo is consistently prioritizing is his own personal political ambitions as opposed to what’s actually good for the country’s long-term national interests or the institutional well-being of the State Department,” added Mr. Weiss, now at the Carnegie Endowment for International Peace.

The recent wave of criticism has made Mr. Pompeo, known for a short fuse, even more testy in public. When a reporter asked Mr. Pompeo whether Mr. Trump’s abandonment of Kurdish partners in Syria had undercut American credibility, he lashed out, saying, “The whole predicate of your question is insane.”

A battered diplomatic corps is finding some solace in the nomination by Mr. Trump and Mr. Pompeo last Thursday of their North Korea envoy, Stephen E. Biegun, as the deputy secretary of state. Mr. Biegun is a longtime national security professional who worked for Condoleezza Rice in the Bush administration.