Former FBI Director James Comey is set to give his long-awaited testimony before the Senate Intelligence Committee on Thursday, in a session that could go down as one of the most-watched and dramatic Hill hearings in recent memory.

Senators will have a mountain of questions for the ex-FBI boss who was fired by President Trump and is now at the center of speculation over whether the president pressured him to stifle Russia-related investigations.

Asked Tuesday about the upcoming hearing, President Trump simply said: "I wish him luck."

Here’s what you need to know:

Hearing Details

There are actually two Senate Intelligence Committee hearings to keep an eye on this week.

The first will be Wednesday at 10 a.m. ET, featuring: Deputy Attorney General Rod Rosenstein; Director of National Intelligence Daniel Coats; Acting FBI Director Andrew McCabe; and National Security Agency Director Adm. Mike Rogers. The hearing technically is on the Foreign Intelligence Surveillance Act, or FISA, and witnesses are expected to testify on laws regarding the collection of foreign intelligence. They will likely face questions about Section 702, which authorizes the intelligence community to target communications of non-U.S. persons located outside the U.S. for foreign intelligence purposes.

While the hearing is set to focus on FISA, the witness panel is rich with people close to the ongoing probe of Russian meddling and potential Trump campaign coordination with Russian officials. Should the hearing delve into that topic, it will serve as a prelude to the big event on Thursday.

That’s when, at 10 a.m. ET in the Senate Hart Building, Comey will testify before the same committee.

The testimony will be carried live on Fox News Channel and FoxNews.com and could last hours.

Why Is Comey Testifying?

The Intelligence Committee has been looking into the Russia issue since early January, in an effort to review the details that informed the intelligence community’s official assessment issued before the Trump administration took office.

It is in this context that the committee originally sought to hear from him on May 11 – however, Comey was fired by Trump in advance of that hearing and McCabe took his place.

Now, Comey is set to return, and the context is much different.

Senators will want to know about the Russia controversy, but will also have questions about the raft of reports regarding the circumstances of his firing. The New York Times reported last month that Trump told Russian officials the firing relieved “great pressure.” The Times also reported that Comey penned a memo saying Trump had earlier pressed him to drop the investigation of former National Security Adviser Michel Flynn (which Trump has denied).

Reports suggest that Comey indeed is expected to tell the committee that Trump asked him to drop the Flynn probe.

What Lawmakers Want to Know

Perhaps foremost on senators’ minds will be what Trump personally told Comey over the last several months. Sen. Dianne Feinstein, D-Calif., a member of the committee, indicated Tuesday that colleagues will ask the fired FBI boss if they can see the memo and notes he produced around the time of his firing, and noted they could issue a subpoena for those documents.

The official story from the White House last month was that Trump fired Comey after receiving a recommendation from Deputy Attorney General Rosenstein, who felt Comey was unfit to continue leading the nation’s “crown jewel” of law enforcement, after his handling of the Hillary Clinton email case last year.

Trump himself has since indicated he was planning to fire Comey regardless of the DOJ recommendation.

Who to Watch

Senate Intelligence Committee Chairman Richard Burr, R-N.C., and Ranking Member Mark Warner, D-Va., have sought to lead their committee’s investigation in a bipartisan fashion, trying to avoid the kind of turmoil facing their counterparts on the House side.

They will both give opening statements for the hearings Wednesday and Thursday. The Comey hearing will be a key test of whether they can keep the investigation on course, and prevent it from becoming another venue for partisan warfare.

Sen. Feinstein is another member to keep an eye on Thursday. Feinstein told Fox News that Comey “wants to testify,” which is “always helpful” with a witness. She could prove to be a probing questioner, having said on CBS’ “Face the Nation” last month that the reason for Comey’s firing needs to be “clear.”

Sen. Susan Collins, R-Maine, is another member to watch, as a Republican who shows little compunction about questioning the administration. She said on “Face the Nation” that it is “so important” for the committee to hear from Comey.

“The acting director of the FBI also said that there’d not been an attempt to influence the investigation,” Collins said. “And yet, we hear of all these memos ... all of these dinners and meetings between President Trump and the former FBI director. So we need to hear directly from Mr. Comey on these important issues.”

Fox News’ Chad Pergram contributed to this report.