New Orleans (CNN) Progressive leaders gathered at the annual Netroots Nation conference sought to deliver a clear message about the Democratic Party's direction headed into the 2020 presidential race: They won't settle for a moderate to take on President Donald Trump.

The three-day gathering of thousands of progressive activists amounted to a rejection of warnings from the Democratic establishment that their calls for single-payer health care, abolishing Immigration and Customs Enforcement agency and other progressive priorities would alienate moderate and Republican voters who are otherwise inclined to vote against Trump -- both in November's midterm elections and in the 2020 presidential primary.

Alexandria Ocasio-Cortez, the 28-year-old Latina who shocked the political establishment when she ousted the No. 4 House Democrat, New York Rep. Joe Crowley, in a primary this summer, urged Democrats to "come home" to ideas that were first proposed by Franklin D. Roosevelt.

"We are picking up where we left off when we were at our most powerful, when we were at our greatest," she said.

Kevin de León, the California state senate leader who is challenging long-time Democratic Sen. Dianne Feinstein this fall, said progressives are in "a battle for the soul of our nation."

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