Trump has exhibited a remarkable amount of loyalty to Flynn, despite ultimately firing him. Flynn’s ouster came a full 18 days after the acting attorney general at the time, Sally Yates, warned the White House that his talks with Russia made him susceptible to blackmail. Trump was “stampeded into” firing Flynn, said Roger Stone, a longtime Trump confidant who is himself under scrutiny in the Russia probe.

“I think he likes Flynn, and he thinks he did him a disservice,” Stone said. “On the other hand we don’t know what Flynn has done, if anything, in addition to the things we know.”

“They got so close during the campaign,” said a senior White House official who was brought on by Flynn and has stayed after his departure. When Flynn left, “the real person who probably took it hardest was the president because General Flynn was the person closest to him on national-security matters.”

Flynn was asked to resign on February 13 after it was publicly revealed that he had lied about his contacts with the Russian ambassador, including to Vice President Mike Pence, who had gone on television defending him. He was replaced by H.R. McMaster, a decorated and respected general who cleared out some Flynn appointees but kept others on the National Security Council.

But Flynn has continued to percolate around the edges of this administration. On March 31, his lawyer Robert Kelner released a statement saying that Flynn would testify in exchange for immunity. “General Flynn certainly has a story to tell, and he very much wants to tell it, should the circumstances permit,” Kelner wrote.

Trump “has questioned whether he should have fired Flynn,” a source close to the White House told The Atlantic last week. “They don’t know what Flynn's going to say."

Flynn had joined the campaign at a time when many other Republicans were still steering clear. He wholeheartedly embraced Trumpian politics, famously leading a “lock her up” chant at the Republican convention. Flynn had come on to advise the campaign during the primaries, and was even considered for the running-mate slot.

In some ways, it was an unlikely relationship; Flynn had been a registered Democrat, and although he had had a long and storied career in the military, he had left under less-than-stellar terms after then-President Barack Obama dismissed him from his post as head of the Defense Intelligence Agency.* In recent years, Flynn had shown a tendency toward Islamophobic sentiment and a weakness for conspiracy theories. But Trump’s affinity for Flynn appears to have been unshaken. Trump has shown a fondness for generals, and has picked several for his administration: Secretary of Defense Jim Mattis, Secretary of Homeland Security John Kelly, and, after Flynn was given the boot, McMaster.

The Trump people can’t say they weren’t warned. (Indeed, Obama is reported to have explicitly warned Trump not to hire Flynn in a meeting during the transition.) “We all knew Flynn had issues,” a senior White House official told me last month. During the transition, Flynn became a frequent story, especially when news outlets discovered his son’s Twitter account which pushed Pizzagate conspiracy theories and interacted with figures on the alt-right.