 -- Progressive organizations are ramping up their campaign against President Trump's Supreme Court nominee, Neil Gorsuch, and calling on Senate Democrats to do more to oppose his confirmation.

On Monday, leading organizations on the left — including MoveOn, UltraViolet and NARAL Pro-Choice America — sent emails to their millions of members asking them to demand that Democrats filibuster any vote to confirm Gorsuch. The push came as the Senate Judiciary Committee today began its confirmation hearing for Gorsuch.

While the majority of Democrats are expected to oppose Gorsuch's confirmation, there has been palpable frustration among progressive activists that more Democratic senators have not yet publicly declared which way they intend to vote. Progressives wanted commitments even before questioning of Gorsuch is completed.

"We're not hearing from enough of the Democratic senators that they will fight this nomination with everything they have. We need them to understand that simply stating their opposition to Neil Gorsuch is not enough," NARAL President Ilyse Hogue wrote in an email to the group's list that went out this morning. "We need Senate Democrats to filibuster this nomination and demand a nominee who represents the mainstream values of our country."

Last week, Senate Minority Leader Chuck Schumer of New York held a press conference with individuals he argued were hurt by Gorsuch's rulings. Still, he would not definitively say he planned to vote against the judge. Schumer said that he has a "strong presumption against" Gorsuch but that he would wait until after he heard the judge's testimony before making up his mind.

Sen. Richard Blumenthal of Connecticut, a senior Democrat on the Judiciary Committee, echoed Schumer. Blumenthal said that he was prepared to filibuster Gorsuch if he was not satisfied with the judge's answers before the committee but that he has a "profound duty" to question Gorsuch before announcing his final decision. Blumenthal added that he prepared "tough but respectful" questions for the hearing this week.

In 2013, when Democrats were in the majority in the Senate, they changed the chamber's rules so that federal judges could be confirmed with a simple majority vote, but they maintained the long-standing requirement that Supreme Court picks need at least 60 votes to end a filibuster and move their confirmation forward.

In order to get those 60 votes, Gorsuch will need at least eight Democrats to vote with Republicans, assuming all Republicans back him. But because the vote with the 60-vote threshold is technically a procedural vote, some Democrats may be tempted to vote in favor of him as a compromise and not risk being labeled obstructionist.

Trump has said that if Democrats slow the process, Majority Leader Mitch McConnell of Kentucky should consider the so-called nuclear option and change the rules to allow a vote to proceed without the 60-vote minimum. Schumer said last week that he did not think Republicans want to go that route.

Some Democrats have already been vocal about their opposition to Gorsuch, including Sens. Jeff Merkley of Oregon and Elizabeth Warren and Ed Markey of Massachusetts. They joined advocacy organizations for an event in front of the Supreme Court last week.

"When Justice Scalia died, giant corporations and their right-wing buddies spent millions of dollars to keep that Supreme Court seat open so Donald Trump could name a replacement. Why? Because giant corporations and their right-wing buddies don't want a neutral court that simply upholds the law for everyone," Warren said at the event. "They want a court that favor corporations over real people. And we are here today to fight back."

There is still a lot of resentment among Democrats that Republicans kept President Obama's nominee Judge Merrick Garland from even getting a hearing. After the event in front of the court last week, volunteers and staffers delivered petitions with over a million signatures, they said, urging senators from both parties to oppose Gorsuch's confirmation.

Progressive groups are quick to point out Gorsuch's conservative record on social issues, including his high-profile ruling in the Hobby Lobby case, in which he sided with a religious employers in their case against a Obama-era mandate to provide contraceptive coverage in health insurance plans. Other Democrats would rather focus on what they say is Gorsuch's record of backing Big Business over workers' rights.

All the witnesses that Schumer took to the Hill last week were plaintiffs in cases in which Gorsuch sided with employers over employees.