Former FBI Director James Comey launched Sessions into the spotlight with his own testimony last week. Now Sessions will take the same stage. Lawmakers have already aired many of their concerns about their former colleague -- from his meetings with the Russian ambassador to the US to his role in the firing of Comey.
And then an ally of President Donald Trump suggested the President is thinking about firing the special counsel investigating the Russia issue.
There's lots of questions for Sessions. Here are six:
Sessions recused himself from overseeing the federal probe into ties between the Trump campaign and Russian officials, just a day after The Washington Post reported that he had two undisclosed meetings with Sergey Kislyak, the Russian ambassador to the US.
But reports of a possible third meeting between Sessions and Kislyak have occupied congressional investigators since then. Comey, according to sources, told senators that investigators overheard Russians discussing a third, private meeting Sessions had with Kislyak. (Sessions' spokespeople have denied a third meeting happened.)
Two Democrats on the Senate Judiciary Committee -- Sens. Al Franken and Patrick Leahy -- who initially pressed Sessions in his confirmation hearings on Russian contacts -- wrote to Comey seeking an investigation into whether Sessions perjured himself when he said he had no contacts.
2. Why did Comey assume Sessions would recuse himself earlier than he did?
While answering questions about why he didn't alert other officials about Trump's request that he end his investigation of former national security adviser Michael Flynn, Comey said that FBI officials long expected Sessions to recuse himself from overseeing the Russia probe.
"Our judgment, as I recall, was that he was very close to and inevitably going to recuse himself for a variety of reasons. We also were aware of facts that I can't discuss in an open setting that would make his continued engagement in a Russia-related investigation problematic," Comey said.
The "variety of reasons" line, followed by admonishment that he couldn't discuss the answer in an open setting perked a lot of ears. Why would Comey think Sessions was going to recuse himself?
3. Will Sessions invoke executive privilege?
The view of the US attorney general coming before a group of aggressive senators may paint a picture similar to the media bonanza of Comey's blockbuster hearing last week. But it's more likely to resemble the public hearing that happened just a day before Comey, where four top intelligence officials were grilled mercilessly, but offered little information.
At one point, Director of National Intelligence Dan Coats cautioned that he would have to consult with the White House counsel's office before even answering questions in a classified session because they may invoke executive privilege.
It's all led to a critical question of when and if Sessions will cite privilege -- used by presidents to block testimony before Congress by their aides on certain topics.
Even the standard process itself of invoking executive privilege could be jumbled by the Russia probe. Invoking of executive privilege for administration employees is typically formally announced by the attorney general, but it's not exactly clear who would make the formal announcement for Sessions, said Michael Bahar, former Democratic staff director for the House intelligence committee and former White House lawyer.
"Everything is being looked at anew, as of late," said Bahar, who now runs the cybersecurity practice for Eversheds Sutherland US in Washington.
The tool covers discussions with the president, Bahar noted, and could be used to protect discussions of Comey's firing and questions about the President's request to Comey to drop the Flynn investigation.
4. What is Sessions' relationship with Trump like, really?
Sessions and Trump have been close allies for more than a year now -- Sessions was Trump's earliest supporter in the Senate and his top staff became some of Trump's most important advisers.
Also, the two were together on issues like immigration and trade when, at the time, Sessions was often a voice in the wilderness among other Senate Republicans.
That's why the reports last week that Sessions offered to resign over a new, incredible strain between the two, was pretty surprising. Multiple reports have cited sources saying that central to that split was Trump's belief that Sessions should never have recused himself from overseeing the Russia probe. (And, implicitly, that Sessions would be in a position to "lift the cloud" of the Russia investigation if he was still overseeing it.)
Sessions certainly isn't expected to hit his boss while testifying on live television, but look for senators to try and get at how much pressure Trump has put on him.
5. Why was Sessions involved in the firing of Comey if he had stepped aside from the Russia probe?
Sessions stepped aside from the Russia probe on March 2.
But, two months later, he was involved in the firing of the FBI official overseeing that probe. Senate Democrats have been champing at the bit for more than a month now to get an answer to what exactly Sessions meant when he said he was recusing himself.
Sen. Ron Wyden, a member of the intelligence committee, told reporters he plans to press Sessions on his recusal.
"Based on everything I know, this isn't close to what people believe is a real recusal! When you're recusing yourself, you are stepping aside and this sure doesn't look like it," Wyden said, referring to Sessions' involvement in the firing letters to Comey.
"I don't think it compromises sources or methods or in any way harms America's position in the world, so we'll start with that," Wyden said. "But there are a host of issues that relate to his recusal, what he may of known about Mike Flynn, that sort of thing."
6. Would Sessions support firing Mueller?
Newsmax CEO and Trump friend Chris Ruddy rung the alarms Monday, saying that Trump was seriously considering firing Robert Mueller, who is leading the federal Russia probe. But since the President cannot directly fire the special counsel, the question lands squarely at the feet of Sessions and Deputy Attorney General Rod Rosenstein.
This prompts the question, would Sessions support the President and fire the special counsel, if he requested it? But, because Sessions has recused himself, the question could easily fall to Rosenstein. Both officials are testifying on the Hill Tuesday.
And would Sessions and Rosenstein risk being fired themselves and refuse to fire Mueller?
CORRECTION: This story has been updated to correct Michael Bahar's law firm.