These are the Judiciary Committee Senators to watch during attorney general nominee William Barr's confirmation hearings

• On Jan. 15 and 16, the Trump administration's nominee for Attorney General William Barr will appear before the Senate Judiciary Committee for confirmation hearings. 

• Sen. Lindsey Graham of South Carolina, a staunch Trump ally and conservative firebrand, now leads the Committee.
• Some of Barr's controversial comments — combined with the high-stakes nature of the nomination, and hyperpartisan environment in Washington — could lead to some tense partisan clashes on the Committee.
• Here are the key Senators to watch during Barr's confirmation hearings. 

On Jan. 15 and 16, the Trump administration's nominee for Attorney General William Barr will appear before the Senate Judiciary Committee for confirmation hearings. 

Barr, 68, previously served as attorney general in the early 1990s under President George H.W. Bush. Since then, he's worked as a corporate lawyer in private practice. 

While Barr is widely-respected in the conservative legal world, some of his opinions have garnered controversy. Barr came under scrutiny for sending an unsolicited 20-page memo to the DOJ criticizing the Mueller probe's line of investigation into possible obstruction of justice and witness tampering by Trump.

Read more: Meet William Barr: What you need to know about the possible once and future attorney general

The memo called Mueller's inquiry into whether Trump obstructed justice by when he fired FBI director James Comey "legally unsupportable" and "potentially disastrous."

Barr also said Trump's firing of Comey was "the right call," supported Trump's firing of Deputy AG Sally Yates, and expressed concern that special counsel Robert Mueller's team of prosecutors is biased against Democrats. As attorney general, he would oversee the Mueller probe. 

Barr's previous comments around the Mueller probe combined with the high-stakes nature of the nomination, and hyperpartisan environment in Washington could lead to some tense clashes. 

Conservative firebrand and Trump-allied Sen. Lindsey Graham, who made headlines for his angry attack on his colleagues during the Kavanaugh hearings, now leads the Committee. 

Here are the key Senators to watch during Barr's confirmation hearings: 

Newly-named Senate Judiciary Chairman Lindsey Graham

Graham used to be criticized as a "RINO" (Republican-in-name-only) for publicly opposing Trump during the 2016 Republican primary — but now he's one of Trump's staunchest defenders and most loyal surrogates on the Hill.

Graham commanded attention and earned the praise of his fellow Republicans in September during the Judiciary Committee hearings on sexual assault allegations facing Supreme Court Justice Brett Kavanaugh, when he lashed out at his Democratic colleagues and vowed revenge. 

"When you see Sotomayor and Kagan, tell them that Lindsey said hello because I voted for them. I would never do to them what you've done to this guy. This is the most unethical sham since I've been in politics," Graham said, referring to Obama-era nominees Sonia Sotomayor and Elena Kagan.

When Kavanaugh told Graham that he'd "been to hell and then some" over the allegations, Graham angrily responded, "This is not a job interview, this is hell."

Previously, Graham told reporters that Democrats can expect their judicial nominees to also face misconduct allegations in the future. "If this is the new norm, you better watch out for your nominees," he said.

Democratic Sen. Kamala Harris has been accused of hostility against Catholic judicial nominees — and is laying the groundwork for a 2020 presidential campaign.

Sens. Kamala Harris and Mazie Hirono (also a Democrat on the Judiciary Committee), have recently been accused of anti-Catholic bias for questioning whether judicial nominee Brian Buescher's membership in the Catholic fraternal organization Knights of Columbus would compromise his impartiality on the bench.

Barr himself is Roman Catholic, although not known to be a member of the Knights of Columbus.

As Harris embarks on a book tour ahead of a rumored presidential announcement sometime in late January, all eyes will be on whether she questions Barr's faith during the hearings, and whether she takes advantage of the spotlight to bolster her campaign ambitions. 

Democratic Sen. Cory Booker of New Jersey is also reported to be mulling a presidential bid.

During Kavanaugh's initial confirmation hearings, Booker took the dramatic step of threatening to release documents purportedly proving Kavanaugh supported racial profiling.

Booker was mocked by some for then declaring, "this is about the closest I’ll probably ever have in my life to an ‘I am Spartacus’ moment" given that the documents had been released that morning.

The comment was a reference to Stanley Kubrick's 1960 film "Spartacus" about an unsuccessful slave rebellion in ancient Rome. 

Now that Booker is taking steps towards a 2020 presidential bid, political observers will be watching to see if he creates more "Spartacus" moments for himself during Barr's confirmation process.