“Whose house?” they shout.

“Our house!” they answer.

By the time of the vote, they’ve moved across the street to the Supreme Court building. After getting word of the vote, again they rush the steps. Two women climb the statues flanking the steps—“Contemplation of Justice” and “Authority of Law”—for more fist-pumps.

On the steps, Bob Bland, a co-founder of the Women’s March, silently sends a thumbs-up signal to another leader, later boasting: “We took the Supreme Court.” On Friday the Women’s March had tweeted out a photo of Sen. Susan Collins, who cast the deciding vote for Justice Kavanaugh, with “Rape Apologist” written across her image.

In a series of tweets and rally comments, President Trump described the crowd as “an angry left-wing mob” of “professional protesters who are handed expensive signs” and “paid for by [George] Soros and others.” Mr. Trump’s detractors accused him of engaging in conspiracy theories, and even of anti-Semitism against Mr. Soros, a billionaire donor to liberal causes. Yet he has a point. Many Americans genuinely oppose Mr. Trump and Justice Kavanaugh. I am a liberal feminist whose views on abortion and same-sex marriage align with the Democratic Party’s. Yet while most demonstrators are not paid for their efforts, the protests at the Capitol Saturday, and the ones that have included stalking lawmakers inside and outside their offices, are organized by groups of which Mr. Soros is an important patron.

I started following the money for the “resistance” when it was born, hours after Election Day 2016. I have organized my findings in a spreadsheet I have made public. At least 50 of the largest organizations that participated as “partners” in the Jan. 21, 2017, Women’s March had received grants from Mr. Soros’s Open Society Foundations or similar funds in the “House of Soros,” as his philanthropic empire was once called internally. The number of Soros-backed partners has grown to at least 80. At least 20 of the largest groups that led the Saturday anti-Kavanaugh protests have been Open Society grantees.

On Saturday I also studied the fine print on the signs as protesters waved them defiantly at the Capitol and the high court. They came from a familiar list of Democratic interest groups that have received millions from Mr. Soros: the American Civil Liberties Union, the Leadership Conference on Civil and Human Rights, Planned Parenthood, NARAL Pro-Choice America, the Center for Popular Democracy, Human Rights Campaign and on and on. MoveOn.org, a Democratic organizing and lobbying group founded with Soros money, sent its army of partisan followers regular missives that led them to a Google form to ask for train tickets and places to stay.