A coalition of liberal dark money groups and networks is behind efforts to expand the Supreme Court, which some top Democrats have thrown their weight behind in recent weeks.

Sen. Ed Markey, D.-Mass., and Rep. Jerry Nadler, D.-N.Y., are leading congressional efforts to expand the Supreme Court from nine to 13 seats. The Democratic lawmakers were joined by members from activist groups Demand Justice, Take Back the Court and Indivisible as they announced legislation on the matter in mid-April.

Prior to the announcement, those left-wing groups formed a coalition to undo former President Trump's judicial legacy, which included plans of adding justices to the nation’s top court.

The congressional Democrats appearing alongside the judicial activists shows the apparent closeness the activist left has with members of Congress. Each of the groups working to add seats to the Supreme Court is fueled by cash that comes from anonymous donors, making it unclear who is bankrolling the outside pressure campaign.

Demand Justice, the most active group advocating for expanding the Supreme Court, also has ties to President Joe Biden’s top aides. White House press secretary Jen Psaki served as an outside adviser to the group, and Paige Herwig, Biden’s point person on judicial nominations, also worked for the group prior to joining the administration.

Demand Justice is led by former Hillary Clinton aide Brian Fallon, who has close ties to the Democracy Alliance, a group of wealthy Democratic donors co-founded by liberal billionaire George Soros that helps steer the progressive agenda. Soros' Open Society Policy Center, a lobbying arm in his network, donated $2.6 million to Demand Justice around the time of its inception three years ago.

Hungarian-born U.S. investor and philanthropist George Soros looks on after having delivered a speech on the sidelines of the World Economic Forum (WEF) annual meeting, on Jan. 23, 2020, in Davos, eastern Switzerland. (FABRICE COFFRINI/AFP via Getty Images)

Hungarian-born U.S. investor and philanthropist George Soros looks on after having delivered a speech on the sidelines of the World Economic Forum (WEF) annual meeting, on Jan. 23, 2020, in Davos, eastern Switzerland. (FABRICE COFFRINI/AFP via Getty Images)

The judicial advocacy group is layered in secrecy. It is a project of the Sixteen Thirty Fund, a nonprofit incubator that provides its tax and legal status to nonprofits, which allows them to avoid filing publicly available tax forms. The Sixteen Thirty Fund is managed by the Washington, D.C.-based consulting firm Arabella Advisors, which oversees a large network that pulled in $715 million in secretive donations for left-wing groups and causes it houses in 2019 alone.

Other groups in the judicial coalition – such as 51 for 51 and Just Democracy – are supported by the North Fund, another D.C.-based nonprofit incubator, but one that operates on a much smaller scale than that of Arabella. Groups at the North Fund have been propped up with cash from Arabella-managed funds. In 2019, the North Fund received $9.3 million from the Sixteen Thirty Fund, according to tax forms.

These groups are not the only ones in the judicial coalition linked to progressive nonprofit incubators awash in hefty cash from anonymous donors.

Demos Action, another coalition member, is fiscally sponsored by Tides Advocacy, a San Francisco-based subsidiary of the Tides network that raised over $800 million for liberal groups and projects in 2019. Indivisible, also a part of the coalition, was fiscally sponsored by the Tides Foundation but has since broken away to its own entity. Tides has been used as an avenue for donors to push money into funds at Arabella.

U.S. Rep. Jerrold Nadler, D-N.Y., chair of the House Judiciary Committee, speaks during a news conference on April 18 in New York.

U.S. Rep. Jerrold Nadler, D-N.Y., chair of the House Judiciary Committee, speaks during a news conference on April 18 in New York. (AP)

"The liberal dark money groups that helped elect Joe Biden and Senate Democrats have been pushing for court packing for years, and now they want what they paid for: A Supreme Court stacked with politicians in robes that will advance their radical policy agenda," said Carrie Severino, president of the Judicial Crisis Network.

In addition to packing the Supreme Court, the coalition also seeks to impose term limits on judges and expand lower courts.

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Court packing is a long shot to pass in Congress. Biden, who once called packing the Supreme Court a "bonehead" idea, announced a commission in early April that would examine expanding the court and setting term limits for justices, the New York Times reported.

Biden was aided by large sums of dark money during the 2020 elections, including $55 million in funds that was passed through the Sixteen Thirty Fund into pro-Biden super PACs.

Markey's and Nadler’s offices did not respond to requests for comment on their relationships with the liberal advocacy groups by press time.