Probes of the Russian Federation allegations have hung over Trump's presidency since he took office and threaten to overwhelm his policy priorities, with several congressional committees conducting their own investigations of the alleged meddling by Moscow.
Comey is scheduled to appear before the panel Thursday.
"I think the Comey news led to an initial surprise but the rebound was equally swift", said Liz Ann Sonders, chief investment strategist at Charles Schwab & Co.
He finished by stressing "the cloud" that was interfering with his ability to make deals for the country and said he hoped I could find a way to get out that he wasn't being investigated.
Still, Trump supporters say they are willing to step in to help the White House deflect any accusations from Comey. Repeated, explosive media reports of Comey's interactions with the president- many with anonymous sourcing - have left Capitol Hill and the media eager to hear Comey's version of events directly. Meanwhile, the main US networks will interrupt their regularly scheduled programs to broadcast what's expected to be hours of high political drama.
Director of National Intelligence Dan Coats and National Security Agency Director Mike Rogers both separately said that while they won't comment on the specifics of their conversations with Trump, neither had felt pressured from the administration.
But the White House has not provided details of when those three conversations allegedly took place.
Comey wrote that he told the president he could not be considered "reliable" in the way politicians use the word, but "he could always count on me to tell the truth".
"That was true; we did not have an open counter-intelligence case on him".
Putin dismisses US claims about Trump, Russia and elections
He accused the U.S. media of sensationalizing information and using it as a "weapon of war" against Trump. Putin then appeared to defend President Donald Trump by saying, "You created a sensation out of nothing".
"I wish him luck", he said. But Trump has repeatedly interjected himself in law enforcement matters, and never more dramatically than in his private meetings with Comey.
Such a request, some observers say, would at best be considered highly inappropriate and at worst obstruction of justice, a criminal act.
Comey's decision to keep his interactions with Trump a secret from the Justice Department were the latest example of how he set himself apart from the department throughout his tenure at Federal Bureau of Investigation director.
By contrast, Comey recalled "nine one-on-one conversations with President Trump in four months - three in person and six on the phone".
A few moments later, the president said, "I need loyalty, I expect loyalty".
Republican Senator Susan Collins of ME, who is also a member of the Senate intelligence committee, said it will be one of the first questions she asks Comey.
Still, King said he would be surprised if Comey agreed to testify without having something important to say. "I replied that he should give that careful thought because it might create a narrative that we were investigating him personally, which we weren't, and because it was very hard to prove a negative". Trump did not provide specifics about those alleged conversations.
Two weeks later, on February 14, Trump kicked Vice President Mike Pence, Sessions and other senior administration officials out of the Oval Office so he could have his one-on-one conversation with Comey, according to people briefed on one of Comey's memos. More than three-quarters of independents say they trust Trump's statements about Russian Federation "just some" or not at all.