There was evidence of possible intent: when the president cleared the room so he could ask Comey - without the attorney general or his son-in-law present - about the investigation into former national security adviser Michael Flynn's contacts with Russian officials after the 2016 election.
There was the suggestion of quid pro quo: when Trump repeatedly raised the status of Comey's job as he asked for loyalty.
And there was the consequence: when Comey, having not steered investigators away from Flynn, was fired by Trump in May, long before the end of his 10-year term.
Comey, a former prosecutor, did not connect those dots explicitly to allege obstruction. But he posited someone who might.
"I don't think it's for me to say whether the conversation I had with the president was an effort to obstruct," Comey said. "I took it as a very disturbing thing, very concerning, but that's a conclusion I'm sure the special counsel will work towards, to try and understand what the intention was there, and whether that's an offense."
Robert Mueller III, another former FBI director, was appointed special counsel last month and heads the independent investigation into Russia's meddling in the 2016 election.
Post Opinion columnists Ruth Marcus and Jennifer Rubin deconstruct the legal and moral quagmire President Donald Trump faces following fired FBI director James B. Comey's testimony to the Senate Intelligence Committee on June 8. (Adriana Usero / The Washington Post)
Legal analysts said Comey's testimony clarified and bolstered the case that the president obstructed justice - adding rich new color about the former FBI director's interactions with the president.
It might not be the last word. Trump's personal lawyer disputed key portions of Comey's under-oath account, and the president has hinted on Twitter he might have "tapes" of what happened. But Comey said he kept contemporaneous memos, which he was willing to see released. He also said he would not stand in the way of the president's purported recordings also becoming public.
"Release all the tapes," Comey said. "I'm good with it."
Comey's testimony was remarkable for its frankness, and his willingness to reveal his personal reactions to the president along with his view of the facts. Comey said Trump's request that he terminate the Flynn investigation left him "stunned," and it sparked serious conversations among senior leaders at the FBI about what to do next.
"It was of investigative interest to us to try and figure out what just happened with the president's request," Comey said.
Of particular concern, Comey said, was that Trump asked other officials to leave him alone with his FBI director in the Oval Office before saying of Flynn: "He is a good guy. I hope you can let this go."
"Why did he kick everybody out of the Oval Office?" Comey said. "That, to me as an investigator, is a very significant fact."
Kelly Kramer, a white-collar criminal defense attorney at the Mayer Brown law firm, said that point was particularly damaging.
"I think any reasonable prosecutor would look at that and say it implies a consciousness of guilt," Kramer said. "You know this is not something you're supposed to be doing. You're not even willing to do it in front of the attorney general."
Marc Kasowitz, Trump's lawyer, disputed Comey's descriptions of Trump's interactions with the president and said Trump "never pressured Mr. Comey."
Kasowitz said Trump never "directed or suggested that Mr. Comey stop investigating anyone," and he said Trump specifically "never suggested that Mr. Comey 'let Flynn go.' "
"As the president publicly stated the next day, he did say to Mr. Comey, 'General Flynn is a good guy, he has been through a lot' and also 'asked how General Flynn is doing,' " Kasowitz said.
Comey testified that he was skeptical of Trump almost from the outset, and he decided to document their interactions because he was "concerned [Trump] might lie about the nature of our meeting."
Kasowitz said the president "never told Mr. Comey, 'I need loyalty, I expect loyalty.' He never said it in form, and he never said it in substance."
The next month, after a counterterrorism briefing, Comey testified that Trump asked him to stay for a one-on-one conversation. He said both Attorney General Jeff Sessions and Trump's son-in-law and close adviser, Jared Kushner, lingered behind - in Comey's view, because they were leery of what might happen next.
When they left, Comey said, Trump said he hoped Comey would shut down an investigation of Flynn. At the time, Comey said, Flynn was "in legal jeopardy," as agents were investigating him for his contacts with Russians and "whether there were false statements made to government investigators."
Under questioning from Sen. Richard Burr, R-N.C., Comey denied that Trump had asked him to stop the FBI investigation into Russian involvement in the 2016 U.S. elections. But he said the Flynn request was nonetheless "very disturbing" and that other bureau officials were "as shocked and troubled by it as I was."
Comey also said he believed he was fired to affect the Russia probe.
"It's my judgment that I was fired because of the Russia investigation," Comey said. "I was fired, in some way, to change - or the endeavor was to change the way the Russia investigation was being conducted."
Comey allowed, under questioning from Sen. James Risch, R-Idaho, that Trump did not outright give him an order on Flynn.
"He did not direct you to let it go?" Risch asked.
"Not in his words, no," Comey said.
But Comey later said he took the president's assertion as akin to a command.
"I took it as a direction," Comey said. "This is the president of the United States, with me alone, saying 'I hope this.' "
The specific language of Trump's request could be pivotal. In response to a question from Risch, Comey conceded he was not aware of a case where the FBI had charged someone for hoping something.
Cornell University law professor Jens David Ohlin said that he understood "why the Republicans would want to focus on 'hope' versus 'direct,' but I don't think it makes any difference."
"Trump made his wishes clear and fired Comey when his wishes weren't respected," Ohlin said. "It doesn't matter whether it was an order or not. What matters is the action that Trump took when it became clear that Comey was continuing the investigation."
While Mueller could ultimately conclude Trump obstructed justice, previous Justice Department legal opinions say he could not indict or charge a sitting president. Congress, though, could impeach the president.
Barak Cohen, a former federal prosecutor now in private practice at Perkins Coie, said he believed Comey was "walking a fine line" by "trying to convey how he interpreted the president, but also admitting that there might have been other ways to interpret what the president said."
But Comey's assessment of the situation, he said, was critically important.
"He was there; he heard the president's tone and saw his body language - things that shape whatever the president was trying to express," Cohen said. "That's why direct evidence of someone who witnesses an alleged crime is so important."
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)