Washington (CNN) As the Senate prepares to vote this week on Neil Gorsuch's nomination, it's unclear yet whether Republicans will have enough votes to end an expected Democratic filibuster.

Republicans, who have a 52-48 majority, need a total of eight Democrats to get to 60 -- the critical number required to end the filibuster.

If they don't reach 60, they can still get around that filibuster, but it would require taking a highly controversial step to change the Senate rules, a move also known as the nuclear option

Republicans already have three Democrats who will vote with them to end the filibuster, so they need five more of the remaining eight undecided Democrats -- as of Sunday -- to do the same and reach that 60 number.

All eyes will be on those undecideds this week.

It's a diverse mix that includes senior Democrats who've been in the chamber for decades to first-term senators. Most are up for re-election, but a majority of that group is considered fairly safe in their respective states.

Here's a look at the nine undecided Democrats and what they've said recently about Gorsuch:

Sen. Pat Leahy (Vermont) -- Having been elected to office in 1975, Leahy is the most senior Democrat in the Senate. He tweeted Monday that he's generally "never inclined to filibuster" a Supreme Court nominee, even though he stated he doubts he can support Gorsuch in the end. Leahy, a member of the Judiciary Committee, later expressed strong concern about Republicans using the nuclear option, something they'd only do if enough Democrats didn't join them to break the filibuster.

Sen. Mark Warner (Virginia) -- Warner has been a bit busy with his other job as the top Democrat on the Senate intelligence committee . He told reporters earlier this week that he was still reading up on Gorsuch but was concerned about what he called Gorsuch's "evasive answers" in his hearings last week.

Sen. Chris Coons (Delaware) -- Coons is also a member of the Judiciary Committee and has a record of working across the aisle on legislation. He, too, has expressed concern about a change in the Senate rules and has been a part of informal conversations to find a way to avert a course that leads to the nuclear option. Still, Coons appeared highly disappointed in some of Gorsuch's answers last week, and he said on MSNBC that he doubts Gorsuch will be able to get the 60 votes needed to advance through the process.

Sen. Michael Bennet (Colorado) -- Bennet has been quiet this week about how where he'll fall on the filibuster. Bennet hails from the same state as Gorsuch and introduced the federal judge at his hearing last week, along with the state's other senator, Republican Cory Gardner. But Bennet made it clear that he was introducing Gorsuch out of tradition and that he wasn't necessarily signaling how he'd vote.

Sen. Dianne Feinstein (California) -- Feinstein is the top Democrat on the Senate Judiciary Committee and another high ranking Democrat in the Senate, having served since 1992. She said she was disappointed with many of Gorsuch's answers at the hearing and felt he wasn't forthcoming enough. The committee meets again Monday to vote on whether to send Gorsuch to the full Senate (with Republicans outnumbering Democrats on the committee, it's expected Gorsuch will pass). Feinstein told reporters this week that she would wait until next week to make her decision known on the filibuster and how she would vote on Gorsuch's confirmation vote.

Sen. Ben Cardin (Maryland) -- Like Feinstein, Cardin also hasn't announced whether he'll run for re-election. He told CNN this week that he plans to vote against Gorsuch's nomination in the end, but he hasn't made a decision on whether he'll vote to maintain the filibuster. "I'm waiting to see what the Republican leadership (does), how they present the nomination on the floor and how they work with the Democrats. There's still a lot of anxiety out there because of the way they handled the (Merrick) Garland (Supreme Court) nomination. So I will wait to see how they handle this nomination before deciding what I will do on procedural votes."

Sen. Bob Menendez (New Jersey) -- Menendez also hasn't announced a 2018 run but he has reportedly started raising campaign funds. Like Feinstein and Cardin, he's considered safe if he decides to run. The New Jersey senator told reporters that he's still deciding on Gorsuch, but "when I come to a conclusion on how I'm voting on Gorsuch, I'll decide on how I'm voting in the whole process."

Independent Sen. Angus King (Maine) -- While King is an independent, he's considered part of the Democratic caucus. He's been fairly quiet about Gorsuch of late. His seat is also considered safe in 2018.