Democratic presidential candidate Sen. Bernie Sanders, I-Vt., speaks at Georgetown University in Washington, Thursday, Nov. 19, 2015, about the meaning of "democratic socialism" and other topics. (AP / CAROLYN KASTER )

WASHINGTON -- Democratic presidential candidate Bernie Sanders said Thursday that economic security is essential to Americans achieving true freedom, a central tenet in his political philosophy of "democratic socialism."

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The U.S. senator from Vermont said the idea has roots in the legacies of President Franklin D. Roosevelt and the Rev.Martin Luther King Jr.

"Real freedom must include economic security. That was Roosevelt's vision 70 years ago. It is my vision today," Sanders said in a speech at Georgetown University. "It is a vision that we have not yet achieved, and it is time that we did."

Sanders' comments came during a speech about his views as he seeks to challenge fellow candidate Hillary Rodham Clinton for the party's nomination. Clinton currently has a lead over Sanders in national polls and has an edge in Iowa, home of the first presidential caucus.

Clinton in recent days has addressed Sanders' support of a single-payer health care system, which she says will require middle-class Americans to pay higher taxes. Much of Sanders' agenda would be paid for by steep tax increases on high earners and Wall Street transactions. He has said his health care proposal would save families significant amounts of money by eliminating waste in the system.

"Health care should be a right of all people, not a privilege. This is not a radical idea," he said.

In explaining his views, Sanders cited Roosevelt's "Second Bill of Rights" from his 1944 State of the Union address, which asserted Americans should have the right to a job with a living wage, health care, education and economic protections for the elderly.

Clinton also has referred to Roosevelt in her campaign, having formally kicked off her campaign at New York's Roosevelt Island in the spring with a speech that touched on her "four fights," alluding to the "four freedoms" Roosevelt laid out in 1941.

Sanders said Roosevelt was responsible for much of the social safety net enjoyed by millions of Americans today, from Social Security, the federal minimum wage, unemployment insurance, the abolition of child labor, the 40-hour workweek, collective bargaining and strong banking regulations.

He said that at the time, "almost everything he proposed, almost every program, every idea he introduced was called 'socialist.'" But he said the federal government's role in providing economic security for Americans had become "the fabric of our nation and the foundation of the middle class."

Without mentioning Clinton by name, Sanders said his candidacy was based on creating a political revolution of supporters to demand a better deal for the middle class.

He added, "So the next time that you hear me attacked as a socialist -- like tomorrow -- remember this: I don't believe government should take over the grocery store down the street or own the means of production, but I do believe that the middle class and the working families of this country who produce the wealth of this country deserve a decent standard of living."

The address included a reference to what some Democrats view as Clinton's inevitability.

"I am not running for president because it is my turn," Sanders said. "That's not why I'm running for president. But I am running for president in order for all of us to be able to live in a nation of hope and opportunity."

A Section on 11/20/2015