“Look, it’s been a rough environment — the Mueller probe, the investigation into D.O.J. and F.B.I.,” Mr. Gowdy said. “But you go pull the transcripts and you find me the question that even a Democrat lawyer would tell you was unfair, ill founded, not factually predicated.”

Mr. Ratcliffe pledged in a statement on Sunday to “work on behalf of all the public servants who are tirelessly devoted to defending the security and safety of the United States.”

If Mr. Ratcliffe is confirmed, the appointment would deprive the president of one of his ablest allies in the House. Mr. Ratcliffe has played an important role in building the case that the F.B.I. harassed Mr. Trump. Republicans consider Mr. Ratcliffe so important to Mr. Trump’s defense on Capitol Hill that his appointment would have been less likely if they still feared that Democrats would advance an impeachment case against Mr. Trump, said one lawmaker familiar with the president’s thinking.

Mr. Trump, of course, has named other partisans to top intelligence jobs. Secretary of State Mike Pompeo, Mr. Trump’s first C.I.A. director, had a reputation as a strong skeptic of the Iran nuclear deal and a critic of the Obama administration’s handling of the Benghazi attacks.

But Mr. Pompeo appointed Ms. Haspel, an agency veteran, as his deputy and quickly came to rely on her expertise, signaling to the C.I.A. rank and file that he valued intelligence professionals.

Mr. Ratcliffe, however, has indicated that he intends to clean house, according to people familiar with his plans. The fate of Mr. Coats’s deputy, Sue Gordon, who runs the office’s day-to-day operations, is unclear. The White House did not immediately announce that she would serve as the acting director when Mr. Coats departs on Aug. 15, as is typical.

Republicans on the House Intelligence Committee have long been pushing for an overhaul of the Office of the Director of National Intelligence, eliminating jobs, slimming the agency and changing how it operates. Mr. Ratcliffe, according to American officials, is likely to try to push through some of those changes if confirmed.