Sen. Kamala Harris Kamala HarrisHarris honors Ginsburg, visits Supreme Court The Hill's Campaign Report: Trump and Biden vie for Minnesota | Early voting begins in four states | Blue state GOP governors back Susan Collins Kamala Harris: Black Americans have been 'disproportionately harmed' by Trump MORE (D-Calif.) on Monday endorsed the "Green New Deal," a proposal that sets a goal of getting 100 percent of U.S. electricity from renewable energy.

"I support a Green New Deal," she said during a CNN town hall in Iowa.

"Climate change is an existential threat to us, and we have got to deal with the reality of it," she added.

Harris, who hadn't previously thrown her support behind the proposal popularized by freshman Rep. Alexandria Ocasio-Cortez Alexandria Ocasio-CortezLawmakers fear voter backlash over failure to reach COVID-19 relief deal Why Democrats must confront extreme left wing incitement to violence The Hill Interview: Jerry Brown on climate disasters, COVID-19 and Biden's 'Rooseveltian moment' MORE (D-N.Y.), doubled down on the endorsement in a tweet Monday night following her remark at the town hall.

"I support a Green New Deal. Climate change is an existential threat to all of us, and we have got to deal with the reality of it," she tweeted.

“I support a Green New Deal … Climate change is an existential threat to us and we have got to deal with the reality of it,” Kamala Harris says. #HarrisTownHall https://t.co/0EMGUsQFut pic.twitter.com/HJIG0HFQDr — CNN (@CNN) January 29, 2019

I support a Green New Deal. Climate change is an existential threat to all of us, and we have got to deal with the reality of it. — Kamala Harris (@KamalaHarris) January 29, 2019

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Harris became the latest high-profile Democrat and 2020 presidential candidate to indicate some level of support for the Green New Deal, joining Sens. Kirsten Gillibrand Kirsten GillibrandSunday shows preview: Justice Ginsburg dies, sparking partisan battle over vacancy before election Suburban moms are going to decide the 2020 election Jon Stewart urges Congress to help veterans exposed to burn pits MORE (D-N.Y.) and Elizabeth Warren Elizabeth WarrenBiden's fiscal program: What is the likely market impact? Warren, Schumer introduce plan for next president to cancel ,000 in student debt The Hill's 12:30 Report - Presented by Facebook - Don't expect a government check anytime soon MORE (D-Mass.) as well as former Housing and Urban Development Secretary Julián Castro.

Harris, Gillibrand, Warren and Castro are also each running or exploring a run for president.

The Green New Deal has attracted the support of a number of progressives. Last year, Ocasio-Cortez proposed that House Democrats create a select committee for a Green New Deal. She has pushed for such goals in the new Congress along with Sen. Bernie Sanders Bernie SandersNYT editorial board remembers Ginsburg: She 'will forever have two legacies' Two GOP governors urge Republicans to hold off on Supreme Court nominee Sanders knocks McConnell: He's going against Ginsburg's 'dying wishes' MORE (I-Vt.).

During the town hall Monday night, Harris also said lawmakers "who are in the pocket of big coal and big oil" don't fully understand the risk of climate change and said children "need to be able to breathe clean air and drink clean water."

"I think that the fact that we have policymakers who are in the pockets of big oil and big coal don't fully appreciate the fact that we are looking at something that is presenting an existential threat to our country," Harris said.

"And, listen, all children need to be able to breathe clean air and drink clean water, and we've got to have a commitment to a policy that will allow that to happen for ourselves and our children and our grandchildren. And right now we don't," she added.