The last conversation James Comey had with President Donald Trump before he was fired as FBI director ended on a strange note. As Comey describes it in the statement he prepared for Thursday’s Senate hearing, Trump called him on the morning of April 11 and brought up a matter he’d raised before: What was Comey doing to sell the public on the idea that Trump wasn’t under investigation by the FBI? When Comey replied that Trump should take it up with the leadership at the Justice Department, the president said he would do so, then continued: “Because I have been very loyal to you, very loyal; we had that thing you know.”
Comey’s statement indicates that he “did not reply or ask him what he meant by 'that thing.' " If Comey won’t ask, we will: What did Trump mean? What was the thing? Let’s consider the possibilities:
1) As I read it, the overall thrust of the April 11 remark was something like, Fine, I will take this up with the leadership of the DOJ, but given how good I’ve been to you, I really think you owe it to me to take care of it yourself.
It’s possible, under that interpretation, that Trump was reminding Comey of the private dinner they’d shared in the White House on Jan. 27, during which Trump twice told Comey that he needed his “loyalty.” According to Comey’s statement, the then-FBI director initially looked at Trump without saying anything; as he describes it, “I didn’t move, speak, or change my facial expression in any way during the awkward silence that followed.” The second time Trump brought up loyalty, Comey told the president he could expect “honesty.” Trump responded, “That’s what I want, honest loyalty,” to which Comey reluctantly agreed.
Maybe that’s the “thing” Trump was alluding to: an imaginary agreement Trump thought he’d made with Comey over dinner. “We had that thing,” under this interpretation, means something along the lines of, I’ve been loyal to you, because you said you’d be loyal to me—I thought we had an understanding.
2) Trump could have been referring to the fateful letter Comey sent 11 days before the election, in which he informed Congress that the Hillary Clinton email investigation had been reopened. The letter prompted Trump to tell the New York Times, “I think it’s the biggest story since Watergate. … I think this changes everything.” According to FiveThirtyEight, the letter also probably cost Clinton the election. It stands to reason Trump was grateful for that letter, especially in light of the affection he showed Comey in the months that followed. (At one point after the election, Trump appeared to blow Comey a kiss and tried unsuccessfully to hug him.)
Trump is a transactional person. It’s possible he considered himself in Comey’s debt on account of "that thing"—meaning that letter he'd sent to Congress—and therefore felt he owed him his loyalty.
3) The two interpretations above both presume “that thing” to be a stand-in for the reason Trump was “very loyal” to Comey. But what if it was actually a reference to something unpleasant that happened between Trump and Comey, and which Trump had been gallantly willing to overlook? Maybe, in other words, Trump was trying to suggest he had been “very loyal” to Comey despite "that thing"—despite, say, Comey’s refusal to “let go” of the Michael Flynn investigation—and had expected better treatment from him in return.
4) It’s Trump. It’s totally possible he didn’t mean anything and was just saying words. “That thing, you know” is a pretty convenient way to trail off at the end of a sentence when you’ve lost your train of thought.