Sen. Elizabeth Warren (D-Mass.) is reiterating her warnings about what's at stake with President Donald Trump picking his Supreme Court nominee "off a pre-approved extremist list," while progressive groups get ready to gather on the courthouse steps in Washington, DC on Monday night to show they're ready "to fight back." 

Trump is expected to make the announcement from the White House at 9pm about who he's chosen to fill the seat left by the retirement of Justice Anthony Kennedy.

In a Monday afternoon tweet, Warren said that all those on the right-wing list have "shown their willingness to side with the wealthy and powerful over the rights of women, workers, voters, and minorities."

Given the stakes, more than a dozen advocacy groups including Indivisible, NARAL Pro-Choice America, and the Leadership Conference on Civil and Human Rights have organized a rally to #SaveSCOTUS, with their action set to begin 30 minutes after Trump makes his announcement.

The Supreme Court heading further right, the groups state, will "ensure that Trump's extreme views are imposed on our country not just for four or eight years, but for decades to come. We can't sit back and let that happen." Their call-to-action adds:

During the campaign, Trump let far-right groups create his list of potential Supreme Court nominees so he could guarantee them that his nominees would overturn Roe v. Wade, criminalize abortion, and punish women. The candidates they selected will vote to gut the Affordable Care Act and take away healthcare from people with pre-existing conditions. And candidates they selected would threaten Americans' civil liberties by upholding discriminatory measures that will undermine LGBTQ equality, make it harder for people of color to vote, make it more difficult for people who have been discriminated against to have their day in court, and even harder for workers to organize for better wages.

As the "Constitutionally-protected right to safe and legal abortion has never faced a greater threat"—despite American voters' overwhelming support for it—reproductive rights groups are sounding the alarm and pointing to the records of the two people who are reportedly the top contenders—Judges Thomas Hardiman and Brett Kavanaugh. 

Some groups are also mobilizing to put pressure on Senate Democrats—with Senate Minority Leader Chuck Schumer the target of a rally Monday evening in his homestate of New York.

"Trump is committed to placing an extreme ideologue on the court, who could endanger environmental protections, overturn Roe v. Wade, and undermine protections for people with pre-existing conditions," said Erich Pica, president of Friends of the Earth.

"If the Senate confirms Trump's nominee, we will be stuck with a court that sides with big corporations over the American people," he continued. "The air we breathe, the water we drink, and the future of our planet is at risk. Any senator who is serious about protecting the environment and fighting climate change must vote against confirmation. Senate Democrats must use everything in their power to keep Trump's dangerous nominees off the Supreme Court."