Though he was reluctant, then-Secretary of Defense Jim Mattis and Gen. Joseph Dunford, the chairman of the Joint Chiefs of staff, convinced him. “He is not the kind of guy who says ‘no’ when called upon to serve,” said Nicholas J. Rasmussen, Mr. Maguire’s predecessor at the counterterrorism center.
Senator Rand Paul, Republican of Kentucky, blocked Mr. Maguire’s nomination for months, seeking information on the targeting of Islamic State militants. By the time the Senate approved the nomination at the end of 2018, Mr. Mattis was gone from government.
Mr. Maguire has been “unflappable” through the current crisis, Mr. Rasmussen said.
“That comes from being someone who has been in much more consequential and stressful situations,” Mr. Rasmussen said. “The idea he would be shaken to the core by a controversy like this I find not credible. Knowing Joe, he’s focused simply on doing the right thing as he understands it.”
Mr. Maguire was not the president’s first choice when his first director of national intelligence, Dan Coats, decided to step down after his relationship with Mr. Trump frayed. The president said this summer that he intended to nominate Representative John Ratcliffe, Republican of Texas, to fill the job.
But Mr. Ratcliffe was seen as highly partisan and had exaggerated parts of his resume. Republicans were also cool to his nomination and Mr. Ratcliffe withdrew. Instead, the White House, which had also forced out Mr. Coats’ deputy, Sue Gordon, turned to Mr. Maguire to serve on an acting basis.
Mr. Trump’s advisers saw him as a safe, experienced choice.
“Everyone who has served with Joe holds him in the highest regarded because he is a person of uncompromising integrity,” said William H. McRaven, former special operations commander who is a longtime friend of Mr. Maguire. “He knows that his loyalty is to the Constitution and the people of this country.”
Mr. Maguire won praise within the intelligence agencies for comments praising Ms. Gordon and saying she had deserved the post.