Eleven progressive groups came together Monday to harshly criticize Senate Democrats for not fighting hard enough against President Donald Trump’s Supreme Court pick Neil Gorsuch, and hinted at primary challenges for any Democrat who votes yes.

“Democrats have failed to demonstrate a strong, unified resistance to this nominee, despite the fact that he is an ultra-conservative jurist who will undermine our basic freedoms and threaten the independence of the federal judiciary,” wrote the groups, including NARAL Pro-Choice America, MoveOn.org, SEIU, Working Families Party, 350 Action, CREDO Action, and others. “We need you to do better.”

These groups represent a wide spectrum of the liberal advocates on a range of issues including labor, abortion rights, the environment, and LGBTQ rights, and very much reflect the liberal base of the Democratic Party.

They also hinted that there will be consequences for Democrats who vote yes. “Democrats who vote yes on cloture or on Gorsuch’s confirmation will be held accountable by their constituents and by the progressive base of the Democratic Party,” CREDO Political Director Murshed Zaheed said in a statement to VICE News.

“There are lots of climate activists across the country who are ready to support primary candidates who take on Democrats who aren’t standing up to Trump,” added May Boeve, executive director of environmental organization 350 Action, in a statement. “People know that we’re running out of time to prevent climate catastrophe and can’t be messing around with politicians who aren’t ready to lead.”

Senate Democrats have been divided so far on how to approach Gorsuch’s nomination. Most are publicly saying they’re keeping an open mind, and some announced their opposition long ago. “The base wants me to reject him out of hand,” Senator Richard J. Durbin of Illinois, the second-highest-ranking Democrat, told the New York Times last month. “I don’t think that serves the country well.”

“Whatever else you can say about [Gorsuch], my sense from his record is, he’s exceedingly independent,” Sen. Angus King of Maine, an Independent who caucuses with the Democrats, told a town hall last night, according to Politico. Angus added that he doesn’t think Gorsuch “should be strictly judged on the idea that it’s Mr. Trump’s nominee.”

The signees of the letter disagree. “Now is the moment to drive up a strong message against Gorsuch,” a NARAL spokesman told VICE News. “There seems to be a desire on the Hill to wait until the hearing, but we need an aggressive and coordinated effort now to point out how conservative he is.”

A minority of senators including Elizabeth Warren of Massachusetts, Sherrod Brown of Ohio, and Jeff Merkley and Ron Wyden of Oregon announced their opposition to Gorsuch the night Trump nominated him to succeed Antonin Scalia, who died in February of 2016. Merkley in particular has argued that Democrats should only vote to confirm Merrick Garland, whom President Obama nominated soon after Scalia’s death and Senate Republicans blocked.

Some Democrats have instead proudly said they will not obstruct the same way the Republicans did last year. Sen. Chris Coons of Delaware issued a press release last month headlined with his quote: “I am not going to do to Judge Neil Gorsuch what Republicans did to Merrick Garland.”

As the Senate rules currently stand, 60 votes are required to break a filibuster, and Republicans only have 52. In order to confirm Gorsuch, Republicans need at least 8 Democrats to vote for him or they will need to invoke the so-called “nuclear option,” which will change the filibuster rules to require only a majority vote. President Trump has encouraged Senate Republicans to use that option if Democrats obstruct, but it’s unclear if enough Republican senators are willing to do away with the filibuster.