As Supreme Court nominee Neil Gorsuch enters his second day of confirmation hearings in the Senate, his fate is dependent upon the support of Democratic senators who are embroiled in partisan fighting over the politics of the high court and a controversial president.

Democrats' concerns could lead to an explosive fight on the Senate floor that would hold up his nomination and potentially force Republicans to enact the so-called "nuclear option," a procedural move that would blow up Senate rules to pass President Donald Trump's nominee.

Operating in a hyper-partisan era with an unpopular new president, Gorsuch’s judicial leanings will be one area of focus for Democrats, but hard feelings felt by Democrats over Republicans blocking the last Supreme Court nominee and Gorsuch's independence from President Donald Trump are other areas of concern.

For now, it appears Republicans have the votes to get their nominee confirmed but it remains to be seen just how far they will need to go to get there. Here's a look at the major factors at play:

An Independent Judiciary

Trump’s attacks on the judiciary has complicated things for his nominee. While Gorsuch, currently a judge on the 10th circuit court, has been preparing for the confirmation process, Trump has made comments that appear to diminish the crucial role of the judiciary overall. Gorsuch has called those attacks “disheartening,” but Sen. Richard Blumenthal, D-Conn., who is one of Gorsuch’s most outspoken critics, said that the nominee has yet to prove that he would truly act independently from the president.

"We meet this week in a looming constitutional crisis,” Blumenthal said during his opening statement before the Senate Judiciary Committee Monday. “Just hours ago, not far from here, the director of the FBI revealed that his agency is investigating potential ties between Pres. Trump's associates and Russian meddling in our election. The possibility of the Supreme Court needing to enforce a subpoena against the president is no longer idle speculation."

Related: Neil Gorsuch Presents Himself as a Consensus Builder as Hearings Begin

Even one Republican senator has voiced concerns about Gorsuch’s independence from Trump and the executive branch.

“I’m interested mostly in his view about the separation of powers,” Sen. Jeff Flake, R-Arizona, told reporters as he walked into the hearing room in a Senate office building Monday morning.

The Politics

But it’s Democrats who will almost certainly decide Gorsuch’s course in the senate. Both Sens. Blumenthal and Jeff Merkley, D-Oregon, have said they are willing to attempt to block Gorsuch’s nomination and a handful of others have already come out in opposition, including Sens. Cory Booker of New Jersey and Sherrod Brown of Ohio. Senate Minority Leader Chuck Schumer has been highly skeptical of Gorsuch.

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Gorsuch needs the support of 60 senators to clear a key procedural hurdle called cloture. With only 52 Republicans, at least eight Democrats will have to support him in that effort. There are a handful of Democrats, mostly who face tough reelections next year, who could support him, including Sens. Joe Manchin of W.V. and Heidi Heitkamp of N.D. Whether there are enough to get to 60 votes remains unclear.

Republicans can change the Senate rules, however, to require only a simple majority, a tactic known as going “nuclear,” which is something that Trump has encouraged. But Senate Majority Leader Mitch McConnell won’t publicly entertain the idea — yet.

Former Democratic Majority Leader Harry Reid used this maneuver for cabinet nominations when President Obama was in office, something that Schumer has said he regrets now that he leads the minority.

Whether now-Majority Leader Mitch McConnell will follow suit remains the biggest question for the Gorsuch vote because doing so would change Senate rules going forward for Supreme Court nominees, impacting the minority party's ability to influence the process in the years ahead.

Open Wounds From Garland Nomination

Democrats are have another issue of concern that, again, doesn’t have anything to do directly with Gorsuch — Merrick Garland, President Obama's nominee for the same seat who never received a hearing from the GOP-controlled senate.

When Justice Antonin Scalia died more than a year ago, leaving the court with only eight justices, then-President Obama nominated Garland, a center-left judge, to fill the opening.

But McConnell's GOP blocked the Senate from taking up the nomination, a move that while successful in preventing Garland from being elevated to the high court, left Democrats bitter.

"As you know, I played arguably the single biggest role in having the vacancy there,” McConnell said at Politico Playbook breakfast earlier this month.

And McConnell said the move helped Trump win the election. “And politically, oddly enough, not only did it not hurt our guys who were running, it actually helped the president bring Republicans home, and he ended up getting 90 percent of the Republican vote, just like Mitt Romney did, and the single biggest issue was, 'who do I want to make this Supreme Court appointment.'"

Democrats are entering Gorsuch’s confirmation hearing with that episode still fresh in their minds — not only was Obama blocked from getting his nominee, but at least McConnell, one of the best political strategists in Washington, thinks Trump won because of it.

Such grudges don’t die easily and at least three Democrats mentioned Garland in their opening statements on the first day of the hearing Monday.

And Neal Katyal, the solicitor general for President Obama, gave a glowing testimony to the Senate Judiciary Committee on Gorsuch’s behalf Monday, but he said Democrats’ anger over the blockade against Garland is legitimate.

“It’s a tragedy of massive proportions that Merrick Garland” was not confirmed to the court, Katyal said, but added that if a member can “be open” to a new nominee, then Gorsuch is a capable and strong candidate.

The Democratic Base

After Trump got most of his very conservative cabinet nominees through (thanks to Reid's use of the nuclear option for those appointees), the Democratic base is energized in their opposition to Gorsuch, putting more pressure on Democratic senators.

Ben Wickler, the Washington director of the progressive group MoveOn, said that Gorsuch is animating its members who have been calling, visiting and emailing senators urging them to oppose the nomination. It’s a campaign that he said will greatly escalate in the next couple of weeks as Gorsuch’s nomination moves through the Senate process, including a national day of action on April 1.

“Between the possible collusion in Russia and the unconstitutional Muslim ban, there’s never been a moment where an independent judiciary has been so critical,” Wickler said. “(Gorsuch) has been hostile to bring any accountability to executive power.”

Garland is being criticized for his role during the George W. Bush administration in interpreting a measure passed by Congress on torture.

"It’s not a question about torture but about presidential authority and the right of any president to ignore a duly passed law or bill passed by congress," Sen. Richard Durbin, D-Illinois.

How all these factors come together for Democratic senators in the days leading up to those votes, and how McConnell decides to use senate rules, could be a bigger factor than anything else about the nominee himself.